Determine and Analyze Central Ideas
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7th Grade ELA › Determine and Analyze Central Ideas
Read the passage and answer the question.
In many cities, summer nights are getting warmer faster than nearby rural areas. One reason is the “urban heat island” effect. Dark roofs and roads absorb sunlight during the day and release that heat slowly after sunset, keeping neighborhoods warmer. Tall buildings can also block wind, which would otherwise carry heat away. Scientists measure this by comparing temperatures from weather stations placed in downtown areas and in parks or farmland outside the city.
City planners are not limited to simply noticing the problem; they can reduce it. Planting more trees adds shade and cools the air through evaporation from leaves. Some cities replace black asphalt with lighter pavement that reflects more sunlight, and they encourage “cool roofs” made from reflective materials. These changes can lower local temperatures and reduce the need for air conditioning.
The passage also explains why this matters for people’s health and budgets. Hotter nights make it harder for bodies to recover from daytime heat, increasing the risk of heat illness, especially for older adults and people without reliable cooling. Higher air-conditioning use can raise electricity bills and strain power grids during heat waves. By combining temperature data with design changes, cities can protect residents and manage energy demand.
Question: Which option best states two central ideas of the passage?
Cities are always hotter than the countryside because the sun shines more strongly on urban neighborhoods.
The passage describes what causes the urban heat island effect and explains ways cities can reduce its impacts on health and energy use.
Air conditioning is the main reason cities stay warm at night, and power grids cannot handle heat waves.
Urban areas have more tall buildings than rural areas, and wind patterns are different in cities.
Explanation
Tests determining two or more central ideas in informational text (main points passage develops, not topic or supporting details), analyzing how ideas develop over course of text (introduction, support through evidence and examples, connections), and providing objective summary (capturing central ideas factually without opinion). Central ideas are specific main points passage develops about topic: Topic is broad subject (climate change, renewable energy, recycling—what text is about generally, one or two words), central ideas are specific assertions or concepts about topic (not just "climate change" but specific ideas: "Human activities cause global warming" and "Climate change produces wide-ranging effects on environment and economy"—specific main points text develops, complete thoughts). Urban heat island passage (300 words). Two central ideas developed: Central Idea 1: Urban heat island effect causes cities to be warmer than rural areas. Developed through: Paragraph 1 explains causes (dark surfaces absorb heat, buildings block wind), provides scientific measurement method (comparing urban vs. rural weather stations), development traced from phenomenon through causes through measurement. Central Idea 2: Cities can reduce heat island impacts through planning and design changes. Developed through: Paragraph 2 identifies solutions (trees for shade/cooling, lighter pavement, reflective roofs), Paragraph 3 explains why this matters (health risks from hot nights, energy costs, power grid strain), development shows problem in Idea 1 leads to solutions in Idea 2 and their importance. Both ideas developed across passage with evidence. Connection: Idea 1 establishes problem (what causes urban heat), Idea 2 provides response (how cities can address it), Paragraph 3 shows why both matter (health and energy impacts)—together provide complete understanding of urban heat phenomenon, solutions, and significance. Option C correctly identifies both central ideas: "describes what causes the urban heat island effect and explains ways cities can reduce its impacts on health and energy use." Options A, B, and D each contain only supporting details (A: tall buildings and wind patterns are specific causes, not central ideas; B: incorrect detail about sun shining more strongly plus supporting detail about air conditioning; D: two supporting details elevated to central status) or factual errors, missing the two main concepts the passage develops comprehensively. Determining and analyzing central ideas: (1) Read complete passage identifying topic (broad subject—what's this about?), (2) distinguish central ideas from topic (not "urban heat" topic but "urban heat island effect causes cities to be warmer" and "cities can reduce impacts through design" specific ideas about topic—what main points does passage make?), (3) identify all central ideas (longer passages often have 2-3—find each main concept passage develops), (4) note supporting details vs. central (dark roofs absorb heat is detail supporting broader heat island idea—levels matter), (5) trace development (how is each central idea introduced, supported with evidence, explained through examples?—follow idea across passage), (6) understand connections (how do multiple central ideas relate building complete understanding?—causes and effects, problems and solutions, different dimensions of topic). Common mistakes include confusing supporting details with central ideas, missing one of multiple central ideas, or failing to see how ideas connect across the passage.
Read the passage and answer the question.
In the late 1800s and early 1900s, many Americans moved from farms to cities for factory jobs. The passage explains that industrialization changed how people worked. In factories, workers often performed one repeated task instead of completing an entire product. This system increased production, but it could also be exhausting and dangerous, especially when machines lacked safety guards.
The passage develops a second idea: these working conditions helped lead to labor organizing. As factories grew, workers realized that one person complaining to a boss rarely changed anything. Groups of workers formed unions to negotiate for shorter hours, safer workplaces, and better pay. Strikes sometimes stopped production and pressured factory owners, although strikes could also lead to conflict with police or replacement workers.
The passage adds that new laws and public attention gradually changed some conditions. Reports about child labor and injuries persuaded some lawmakers to set age limits and require safer equipment. While problems did not disappear, the passage shows how changes in work, collective action, and government responses were connected.
Question: Which option best summarizes the passage objectively?
The passage is mainly about how machines work and why cities are more exciting than farms.
The passage lists every law that ended child labor and completely fixed workplace safety.
The passage proves that factory owners were cruel and that strikes were the only fair solution.
The passage explains how factory work increased production but created harsh conditions, and it describes how unions and laws developed in response.
Explanation
Tests determining two or more central ideas in informational text (main points passage develops, not topic or supporting details), analyzing how ideas develop over course of text (introduction, support through evidence and examples, connections), and providing objective summary (capturing central ideas factually without opinion). Central ideas are specific main points passage develops about topic: Topic is broad subject (climate change, renewable energy, recycling—what text is about generally, one or two words), central ideas are specific assertions or concepts about topic (not just "climate change" but specific ideas: "Human activities cause global warming" and "Climate change produces wide-ranging effects on environment and economy"—specific main points text develops, complete thoughts). Industrialization passage (250 words). Two central ideas developed: Central Idea 1: Industrialization changed how people worked through factory system. Developed through: Paragraph 1 explains shift from farms to factories, describes new work patterns (repeated tasks vs. complete products), notes increased production but also exhaustion/danger. Central Idea 2: Poor working conditions led to labor organizing and eventual reforms. Developed through: Paragraph 2 explains union formation and collective action (strikes, negotiations), Paragraph 3 describes resulting laws and public attention leading to changes (age limits, safety requirements). Connection: Idea 1 establishes conditions that prompted Idea 2's responses—cause and effect relationship showing how industrial changes created problems that sparked organized responses and reforms. Objective summary must capture both ideas factually without opinion or evaluation. Option A provides objective summary: "The passage explains how factory work increased production but created harsh conditions, and it describes how unions and laws developed in response." Uses neutral reporting language ("explains," "describes"), captures both central ideas (factory conditions AND organized responses), appropriate length, no personal opinion or evaluation. Option B adds opinion/evaluation ("proves," "cruel," "only fair solution"); Option C misidentifies central ideas focusing on minor details; Option D overstates content and completeness. Determining and analyzing central ideas: (1) Read complete passage identifying topic (broad subject—what's this about?), (2) distinguish central ideas from topic (not "industrialization" topic but "industrialization changed work patterns" and "poor conditions sparked organizing" specific ideas about topic—what main points does passage make?), (3) identify all central ideas (longer passages often have 2-3—find each main concept passage develops), (4) note supporting details vs. central (repeated tasks, safety guards are details supporting broader ideas—levels matter), (5) trace development (how is each central idea introduced, supported with evidence, explained through examples?—follow idea across passage), (6) understand connections (how do multiple central ideas relate building complete understanding?—causes and effects, problems and solutions, different dimensions of topic). Objective summary requires neutral language reporting what text says, not reader's opinions about whether changes were good/bad, fair/unfair.
Read the passage and answer the question.
Many people think of the Internet as something invisible, but it depends on physical networks. One central idea is that data travels through a layered system of hardware. When you send a message, it may move from your phone to a nearby cell tower or Wi-Fi router, then through cables and switches owned by Internet service providers. Much of the world’s data crosses oceans through fiber-optic cables that carry light signals. These connections must be maintained, protected from damage, and upgraded as demand grows.
A second central idea is that speed and reliability are shaped by choices and limits. The distance data travels can add delay, and crowded networks can slow down during peak hours. Companies place servers closer to users in “data centers” so videos and websites load faster. At the same time, storms, power outages, or construction accidents can interrupt service, which is why networks often include backup routes.
Understanding these two ideas helps explain why some places have faster service than others. Regions with fewer cables or older equipment may struggle, while areas with more investment and redundancy can handle heavy use.
Which choice best identifies the TOPIC of the passage and a CENTRAL IDEA (not just a broad topic)?
Topic: The Internet’s physical infrastructure; Central idea: Data depends on hardware networks like routers, cables, and servers, and these systems affect speed and reliability.
Topic: Storms; Central idea: Storms always break the Internet everywhere.
Topic: Technology; Central idea: Technology is interesting.
Topic: Fiber-optic light; Central idea: Light is faster than sound.
Explanation
This question tests determining two or more central ideas in informational text (main points passage develops, not topic or supporting details), analyzing how ideas develop over course of text (introduction, support through evidence and examples, connections), and providing objective summary (capturing central ideas factually without opinion). Central ideas are specific main points passage develops about topic: Topic is broad subject (climate change, renewable energy, recycling—what text is about generally, one or two words), central ideas are specific assertions or concepts about topic (not just "climate change" but specific ideas: "Human activities cause global warming" and "Climate change produces wide-ranging effects on environment and economy"—specific main points text develops, complete thoughts). This Internet passage distinguishes topic from central idea clearly: Topic is "The Internet's physical infrastructure"—broad subject of what passage discusses. Central idea is specific assertion: "Data depends on hardware networks like routers, cables, and servers, and these systems affect speed and reliability"—specific main point passage develops about the topic. Choice B correctly identifies both: topic names broad subject area, central idea makes specific claim about that subject that passage develops with evidence (details about cell towers, fiber-optic cables, data centers, backup routes all support this central idea). Choice A shows common error: "Technology" too broad for topic, "Technology is interesting" too vague for central idea—not specific assertion passage develops. Choice C picks one detail (fiber-optic light) as topic, makes trivial claim as central idea. Choice D misidentifies topic and invents false central idea about storms. Distinguishing topic from central idea crucial: topic is what text is about (can usually state in few words), central idea is specific main point text makes about that topic (complete thought making assertion).
Read the passage, then answer the question.
In the early 1900s, many American cities were crowded and unhealthy. Trash often piled up in streets, and open sewers spread disease. Reformers in the “public health movement” pushed for cleaner water, better waste removal, and rules for housing. Over time, cities built water-treatment plants and created systems to collect garbage more regularly.
The passage explains that these changes were not only about cleanliness; they were also about preventing illness. When cities filtered and disinfected drinking water, deaths from diseases like typhoid dropped sharply. Health departments began tracking outbreaks, which helped officials respond faster when problems appeared.
However, the passage also shows that progress was uneven. Some neighborhoods received new services sooner than others, often because wealthier areas had more political influence. In addition, building modern systems cost money, so leaders debated taxes and budgets. Even with disagreements, the passage notes that public health reforms reshaped city life by making basic services—like safe water and trash collection—more reliable for many residents.
Which choice is a central idea of the passage, not just a supporting detail?
Trash sometimes piled up in streets in the early 1900s.
Typhoid was one of the diseases affected by cleaner drinking water.
Some leaders debated taxes and budgets.
Cities built water-treatment plants and improved waste removal to reduce disease and improve health.
Explanation
This question tests determining two or more central ideas in informational text (main points passage develops, not topic or supporting details), analyzing how ideas develop over course of text (introduction, support through evidence and examples, connections), and providing objective summary (capturing central ideas factually without opinion). Central ideas are specific main points passage develops about topic: Topic is broad subject (climate change, renewable energy, recycling—what text is about generally, one or two words), central ideas are specific assertions or concepts about topic (not just "climate change" but specific ideas: "Human activities cause global warming" and "Climate change produces wide-ranging effects on environment and economy"—specific main points text develops, complete thoughts). Supporting details are facts, examples, statistics illustrating central ideas (aluminum can be recycled infinitely—specific fact supporting broader central idea that recycling conserves resources; not central itself but supports central). The passage about public health reforms develops central ideas about how cities improved health through infrastructure changes. Choice A states a central idea: "Cities built water-treatment plants and improved waste removal to reduce disease and improve health"—this is a main point the entire passage develops, showing cause (infrastructure improvements) and effect (better health), developed across all three paragraphs with evidence. Choice B "Typhoid was one of the diseases affected" is a supporting detail—specific example illustrating the broader central idea about health improvements, mentioned briefly as evidence not developed as main point. Choice C "Some leaders debated taxes and budgets" is a supporting detail about implementation challenges, not a central idea—brief mention supporting the idea that progress faced obstacles. Choice D "Trash sometimes piled up" is a supporting detail describing conditions before reforms—sets context but isn't a main point passage develops. Distinguishing central ideas from supporting details: central ideas get substantial development (multiple sentences, paragraphs, evidence), represent main assertions passage makes, could stand as thesis statements. Supporting details provide specific examples, facts, or evidence for central ideas but aren't themselves the main points—they illustrate, prove, or elaborate the central ideas. Common mistakes: topic for central idea ("about climate change" vs. "human activity causes warming"), supporting detail for central (treats example as main point), missing multiple central ideas (identifies one, misses others).
Read the passage, then answer the question.
Renewable energy is a broad topic that includes power sources that can be replaced naturally, such as sunlight and wind. The passage explains one central idea: compared to burning coal or oil, generating electricity from wind turbines and solar panels produces far fewer greenhouse gases during operation. Because these technologies do not require fuel to be burned each day, they can reduce the air pollution that contributes to climate change and smog.
A second central idea is that the costs of renewable energy are complicated. Building a wind farm or installing solar panels can require high upfront spending for equipment, permits, and construction. However, once the system is running, the “fuel” is free, and maintenance costs can be predictable. Over many years, this can make the total cost competitive with fossil-fuel plants, especially when fuel prices rise.
The passage adds that communities also have to plan for renewable energy’s challenges. Solar panels do not produce electricity at night, and wind speeds change, so energy storage and updated power grids can help balance supply and demand. The passage concludes that understanding both benefits and costs helps decision-makers choose energy mixes that fit local needs.
Which choice correctly identifies the topic and a central idea from the passage?
Topic: solar panels; Central idea: solar panels only work in deserts.
Topic: climate change; Central idea: wind speeds are always the same.
Topic: electricity bills; Central idea: permits are the only expense of building a wind farm.
Topic: renewable energy; Central idea: renewable sources can reduce greenhouse gas emissions compared to fossil fuels.
Explanation
This question tests determining two or more central ideas in informational text (main points passage develops, not topic or supporting details), analyzing how ideas develop over course of text (introduction, support through evidence and examples, connections), and providing objective summary (capturing central ideas factually without opinion). Central ideas are specific main points passage develops about topic: Topic is broad subject (climate change, renewable energy, recycling—what text is about generally, one or two words), central ideas are specific assertions or concepts about topic (not just "climate change" but specific ideas: "Human activities cause global warming" and "Climate change produces wide-ranging effects on environment and economy"—specific main points text develops, complete thoughts). The passage explicitly distinguishes topic from central ideas in its opening: "Renewable energy is a broad topic" then develops specific central ideas about that topic. Choice B correctly identifies: Topic = "renewable energy" (broad subject, what passage is about generally), Central idea = "renewable sources can reduce greenhouse gas emissions compared to fossil fuels" (specific assertion passage develops with evidence in paragraph 1—not just "renewable energy" but specific claim about renewable energy). This matches passage's first developed central idea about environmental benefits. Choice A incorrectly limits solar panels to deserts—passage doesn't make this claim, discusses solar more broadly. Choice C states "wind speeds are always the same" which contradicts passage saying "wind speeds change"—factually wrong. Choice D focuses on narrow detail (permits) not central idea, and claims it's "only expense" which passage doesn't state. Topic vs. central idea distinction: Topic answers "What is this text about?" in 1-3 words (recycling, climate change, renewable energy). Central idea answers "What specific point does the text make about that topic?" in complete thought ("Recycling reduces environmental impact," "Climate change affects agriculture," "Renewable energy reduces emissions"). Passages develop central ideas with evidence, not topics—topics are just the general subject area.
Read the passage and answer the question.
In some schools, students use “block scheduling,” where classes meet for longer periods but fewer times each week. One central idea about block scheduling is that longer class time can support certain kinds of learning. Teachers may have time for labs, debates, writing workshops, or projects that are hard to complete in a short period. Students can also spend more time practicing a skill while the instructions are still fresh.
A second central idea is that the same schedule can create new challenges. If a student misses a day, they miss a larger chunk of instruction. Some students find it harder to stay focused for a long class, especially if lessons rely only on lecture. In addition, a course that meets only one semester may end months before a final exam, so students may need review to remember material.
Because of these trade-offs, schools often adjust block scheduling rather than using one strict model. Some add short “support periods,” and others alternate days to balance concentration and flexibility.
Which choice best provides an objective summary of the passage?
The passage shows that block scheduling is obviously the best schedule and that any school that disagrees is wrong.
The passage describes block scheduling, explaining that longer periods can allow deeper activities while also creating challenges like missed instruction and focus issues, and it notes that schools may adjust the model to manage these trade-offs.
The passage argues that students should skip school less often because missing a day is unfair to teachers.
The passage is mostly a list of classroom activities, such as debates and labs, and it does not discuss scheduling at all.
Explanation
This question tests determining two or more central ideas in informational text (main points passage develops, not topic or supporting details), analyzing how ideas develop over course of text (introduction, support through evidence and examples, connections), and providing objective summary (capturing central ideas factually without opinion). Central ideas are specific main points passage develops about topic: Topic is broad subject (climate change, renewable energy, recycling—what text is about generally, one or two words), central ideas are specific assertions or concepts about topic (not just "climate change" but specific ideas: "Human activities cause global warming" and "Climate change produces wide-ranging effects on environment and economy"—specific main points text develops, complete thoughts). This block scheduling passage develops two central ideas about the same educational approach: Central Idea 1: Longer periods can support certain kinds of learning. Developed through: examples of activities enabled (labs, debates, workshops), benefit of practicing while instructions fresh. Central Idea 2: Same schedule creates new challenges. Developed through: missing day means larger gap, focus difficulties in long classes, semester courses ending before exams. Final paragraph shows schools adjust to manage trade-offs between benefits and challenges. Choice A provides objective summary capturing both ideas: "longer periods can allow deeper activities" (Idea 1) "while also creating challenges like missed instruction and focus issues" (Idea 2), "schools may adjust the model to manage these trade-offs" (synthesis)—uses neutral language ("describes," "explaining," "notes"), appropriate length, no evaluation. Choice B includes opinion ("obviously the best," "wrong"), Choice C misrepresents content claiming no scheduling discussion, Choice D invents argument about fairness to teachers. Objective summary must report what text says using neutral language, capturing all central ideas without adding opinion or evaluation.
Read the passage, then answer the question.
The passage explains that the brain can change in response to experience, a quality called neuroplasticity. When a person practices a skill—such as playing an instrument or learning new vocabulary—connections between certain neurons can strengthen. Over time, the brain becomes more efficient at sending signals along those pathways, which can make the skill easier.
The passage also develops a second central idea: neuroplasticity does not mean change is effortless. Building new pathways usually requires repeated practice and rest. Sleep helps the brain organize information, and taking breaks can prevent overload. The passage notes that frustration is common because progress can be slow, especially when a skill is complex.
Finally, the passage explains that neuroplasticity can support recovery after injury. In some cases, therapy helps people practice movements or speech so other parts of the brain can take over tasks that were damaged. Although recovery has limits, the passage emphasizes that targeted practice can improve function.
Which statement is best classified as a supporting detail rather than a central idea?
Neuroplasticity can aid learning and can also support recovery after injury through targeted practice.
The brain can change in response to experience, strengthening neural connections with practice.
Changing the brain often requires repeated practice and time rather than happening instantly.
Sleep can help the brain organize information during learning.
Explanation
This question tests determining two or more central ideas in informational text (main points passage develops, not topic or supporting details), analyzing how ideas develop over course of text (introduction, support through evidence and examples, connections), and providing objective summary (capturing central ideas factually without opinion). Central ideas are specific main points passage develops about topic: Topic is broad subject (climate change, renewable energy, recycling—what text is about generally, one or two words), central ideas are specific assertions or concepts about topic (not just "climate change" but specific ideas: "Human activities cause global warming" and "Climate change produces wide-ranging effects on environment and economy"—specific main points text develops, complete thoughts). Supporting details are facts, examples, statistics illustrating central ideas (aluminum can be recycled infinitely—specific fact supporting broader central idea that recycling conserves resources; not central itself but supports central). The passage develops central ideas about neuroplasticity: (1) Brain changes in response to experience through strengthening neural connections, (2) Change requires effort—repeated practice and time, (3) Neuroplasticity supports both learning and injury recovery. Choice A "Sleep can help the brain organize information during learning" is a supporting detail—mentioned briefly in paragraph 2 as one factor in the process, not developed as main point but supporting the central idea that change requires various elements including rest. Choice B describes the basic mechanism of neuroplasticity—part of first central idea. Choice C combines two central ideas (learning and recovery applications). Choice D relates to second central idea about effort required. Distinguishing supporting details from central ideas: Supporting details provide specific facts or examples that illustrate broader points (sleep helping organization is specific factor supporting broader idea about requirements for brain change), while central ideas are main concepts passage develops extensively. Check development level: central ideas get multiple sentences, paragraphs, extensive explanation; supporting details mentioned briefly as evidence or examples. Common mistakes: elevating supporting detail to central idea—treats example as main point when it's actually evidence for larger concept.
Read the passage and answer the question.
Many people think of microbes only as germs, but the passage explains that microbes also play helpful roles in the human body. In the digestive system, communities of bacteria help break down certain foods and produce vitamins. Scientists have found that different diets can change which microbes thrive, which may affect how efficiently the body uses nutrients.
A second central idea is that the balance of microbes can influence health in more than one way. The passage describes research suggesting that some microbes help train the immune system to recognize harmful invaders. When the balance is disrupted—after a strong course of antibiotics, for example—some people may experience digestive problems because beneficial bacteria have been reduced along with harmful ones.
The passage adds that researchers are still learning, so simple answers are rare. While probiotic foods and supplements may help some people, the passage emphasizes that results vary and that medical advice is important for serious conditions.
Question: Which statement best identifies the topic and a central idea of the passage?
Topic: vitamins; Central idea: vitamins are the only reason people need bacteria.
Topic: antibiotics; Central idea: antibiotics should never be used because they always harm the body.
Topic: microbes in the human body; Central idea: helpful microbes support digestion and can affect health by interacting with diet and the immune system.
Topic: immune cells; Central idea: immune cells are microbes that live in the stomach.
Explanation
Tests determining two or more central ideas in informational text (main points passage develops, not topic or supporting details), analyzing how ideas develop over course of text (introduction, support through evidence and examples, connections), and providing objective summary (capturing central ideas factually without opinion). Central ideas are specific main points passage develops about topic: Topic is broad subject (climate change, renewable energy, recycling—what text is about generally, one or two words), central ideas are specific assertions or concepts about topic (not just "climate change" but specific ideas: "Human activities cause global warming" and "Climate change produces wide-ranging effects on environment and economy"—specific main points text develops, complete thoughts). Microbes passage example demonstrates topic vs. central idea distinction. Topic: microbes in the human body (broad subject—what passage is about). Central Idea 1: Helpful microbes play beneficial roles, especially in digestion. Developed through: Paragraph 1 counters "only germs" misconception, explains digestive bacteria roles (breaking down food, producing vitamins), notes diet affects which microbes thrive. Central Idea 2: Microbe balance affects health in multiple ways including immune function. Developed through: Paragraph 2 describes immune system training by microbes, explains disruption effects (antibiotics example), shows broader health connections beyond digestion. Option C correctly identifies topic and central idea: "Topic: microbes in the human body; Central idea: helpful microbes support digestion and can affect health by interacting with diet and the immune system." Shows broad topic (microbes in body) and specific assertion about that topic (they help digestion and affect health through various interactions). Option A narrows topic to vitamins, overstates as "only reason"; Option B wrong topic (antibiotics are example, not topic), extreme false claim; Option D confuses immune cells with microbes. Determining and analyzing central ideas: (1) Read complete passage identifying topic (broad subject—what's this about?), (2) distinguish central ideas from topic (not "microbes" topic but "helpful microbes aid digestion" and "microbe balance affects health" specific ideas about topic—what main points does passage make?), (3) identify all central ideas (longer passages often have 2-3—find each main concept passage develops), (4) note supporting details vs. central (vitamin production is detail supporting broader helpful role idea—levels matter), (5) trace development (how is each central idea introduced, supported with evidence, explained through examples?—follow idea across passage), (6) understand connections (how do multiple central ideas relate building complete understanding?—causes and effects, problems and solutions, different dimensions of topic). Topic identification requires finding broadest subject (microbes in human body), while central ideas are specific claims passage makes about that topic (helpful roles, health effects).
Read the passage and answer the question.
Some farmers are planting cover crops—such as clover, rye, or radishes—not to harvest them, but to improve the soil between main crops. One central idea is that cover crops can protect and rebuild soil. Their roots hold soil in place during heavy rain, reducing erosion. When the plants are later cut and left to decompose, they add organic matter that can improve soil structure.
Another central idea is that cover crops can affect farm economics and management. Buying seed and planting an extra crop costs money and time, and farmers must decide when to plant and when to terminate the cover crop so it does not compete with the main crop for water. Yet cover crops can also reduce costs in other ways. Some types, like legumes, add nitrogen to the soil, which can lower the need for fertilizer. Better soil can absorb water more effectively, which may help fields handle drought or sudden storms.
The passage shows that cover crops are not a simple “free” solution. Instead, they offer environmental benefits while requiring careful planning to fit each farm’s budget and climate.
Which choice best states TWO central ideas of the passage?
Radishes are the most common cover crop everywhere, and nitrogen is only found in fertilizer bags.
Cover crops improve soil by reducing erosion and adding organic matter, and they involve economic and management trade-offs that can create both costs and savings for farmers.
Cover crops are planted mainly for decoration, and they always compete with main crops for water.
The passage’s topic is plants, and the central idea is that plants are important to life on Earth.
Explanation
This question tests determining two or more central ideas in informational text (main points passage develops, not topic or supporting details), analyzing how ideas develop over course of text (introduction, support through evidence and examples, connections), and providing objective summary (capturing central ideas factually without opinion). Central ideas are specific main points passage develops about topic: Topic is broad subject (climate change, renewable energy, recycling—what text is about generally, one or two words), central ideas are specific assertions or concepts about topic (not just "climate change" but specific ideas: "Human activities cause global warming" and "Climate change produces wide-ranging effects on environment and economy"—specific main points text develops, complete thoughts). This cover crops passage develops two central ideas: Central Idea 1: Cover crops improve soil through erosion control and organic matter addition. Developed through: First paragraph explains roots hold soil during rain (erosion control), decomposing plants add organic matter improving structure, environmental benefits detailed. Central Idea 2: Cover crops involve economic and management trade-offs. Developed through: Second paragraph details costs (seed, planting time), management decisions (timing to avoid competition), but also savings (nitrogen from legumes reduces fertilizer need, better water absorption helps with weather extremes), shows both costs and benefits. Choice B correctly identifies both: "Cover crops improve soil by reducing erosion and adding organic matter" (Idea 1), "they involve economic and management trade-offs that can create both costs and savings" (Idea 2). Choice A incorrectly states decoration purpose and only negative competition, Choice C makes false specific claims about radishes and nitrogen, Choice D confuses broad topic with vague central idea. Final paragraph reinforces both ideas: not simple solution but environmental benefits requiring planning—synthesis of both central ideas showing their connection.
Read the passage and answer the question.
When people talk about renewable energy, they often focus on the type of technology—solar panels, wind turbines, or hydropower. The passage explains, however, that the bigger question is what these sources replace. Electricity made by burning coal or natural gas releases carbon dioxide, a greenhouse gas that traps heat in Earth’s atmosphere. In contrast, solar and wind generate electricity without releasing carbon dioxide during operation, so switching to them can lower overall emissions.
The passage also develops a second idea: renewable energy can be expensive at first, but it may save money over time. Building wind farms or installing rooftop solar requires upfront spending for equipment and construction. Yet once installed, the “fuel” for wind and sunlight is free, and maintenance costs can be predictable. Over many years, that can make the total cost competitive with fossil fuels, especially when fuel prices rise.
Finally, the passage notes that renewables require planning. Because wind and sunlight vary, power companies may add batteries, connect to larger regional grids, or keep some flexible power plants available. These steps help ensure electricity is reliable while emissions decrease.
Question: How is the idea that renewable energy can save money over time developed across the passage?
By listing different renewable technologies and explaining how each one works in detail.
By arguing that fossil fuels will disappear soon, making renewables the only possible choice.
By comparing upfront costs with long‑term factors like free fuel and predictable maintenance, showing how total costs can become competitive.
By focusing mainly on how batteries store energy and ignoring costs altogether.
Explanation
Tests determining two or more central ideas in informational text (main points passage develops, not topic or supporting details), analyzing how ideas develop over course of text (introduction, support through evidence and examples, connections), and providing objective summary (capturing central ideas factually without opinion). Central ideas are specific main points passage develops about topic: Topic is broad subject (climate change, renewable energy, recycling—what text is about generally, one or two words), central ideas are specific assertions or concepts about topic (not just "climate change" but specific ideas: "Human activities cause global warming" and "Climate change produces wide-ranging effects on environment and economy"—specific main points text develops, complete thoughts). Renewable energy passage focuses on one central idea: renewable energy can save money over time despite high initial costs. Development traced: Paragraph 2 introduces idea ("renewable energy can be expensive at first, but it may save money over time"), provides supporting evidence (upfront costs for equipment/construction acknowledged), then contrasts with long-term benefits (free "fuel" from wind/sun, predictable maintenance costs), concludes with comparison ("total cost competitive with fossil fuels, especially when fuel prices rise"). Development shows progression from acknowledging initial expense through explaining ongoing savings to final cost comparison. Option B correctly traces this development: "By comparing upfront costs with long-term factors like free fuel and predictable maintenance, showing how total costs can become competitive." Option A incorrect—lists technologies but passage doesn't detail how each works when developing cost idea; Option C incorrect—passage doesn't argue fossil fuels will disappear soon; Option D incorrect—batteries mentioned briefly in different context, not focus of cost development. Determining and analyzing central ideas: (1) Read complete passage identifying topic (broad subject—what's this about?), (2) distinguish central ideas from topic (not "renewable energy" topic but "renewables save money over time" specific idea about topic—what main points does passage make?), (3) identify all central ideas (longer passages often have 2-3—find each main concept passage develops), (4) note supporting details vs. central (free fuel from sun/wind is detail supporting broader cost-saving idea—levels matter), (5) trace development (how is each central idea introduced, supported with evidence, explained through examples?—follow idea across passage), (6) understand connections (how do multiple central ideas relate building complete understanding?—causes and effects, problems and solutions, different dimensions of topic). Development analysis requires following specific idea through passage, noting introduction, evidence provided, examples given, and conclusions drawn—not just identifying idea exists but showing how author builds and supports it systematically.