A "tragedy of the commons" occurs when people exploit natural resources at a rate that is optimally profitable for the individual with no regard to the long-term sustainability or future profit of the resource. Abalone were harvested to near extinction in California because hundreds of individual fishermen were harvesting at a rate that was most profitable to themselves rather than a rate that would be collectively sustainable. Commercial harvest bans and stringent sport regulations are examples of government tackling issues associated with the tragedy of the commons. 

Until the late nineteenth century, environmental law had a heavy focus on westward expansion and increased land use. This trend was largely fueled by the potential wealth from agricultural activity and harvesting wildlife, timber, and minerals in a region that was largely unsettled and had vast natural resources. Since resources were still quite abundant, conservation was a lower priority than expansion at the time. The Homestead Acts ensured that people of all socioeconomic standing were given equal opportunity to settle the western United States. 

The second wave of U.S. environmental law shifted the focus from westward expansion to conservation of wilderness areas for future use and enjoyment. By this time in history, the western United States had become largely settled and conservation of resources became a higher priority. Air quality had not yet become an issue of concern and remained this way until the middle of the twentieth century when the automobiles and subsequent pollution became more commonplace in the American landscape.

Electrical energy is form of energy that results from the motion of electrons.

Nuclear energy has the potential to last a long time; however, the quantity is finite and limited—similar to oil and gas. Solar energy, wind energy, and geothermal energy—from heat within the Earth—are produced by energy sources that do not deplete over time and can be constantly renewed. 

Photosynthesis is the chemical process of utilizing the sun's radiant energy to produce glucose. Glucose is a carbohydrate monomer that is used for energy storage. Heat is not the type of energy utilized from the sun and the conversion of chemical energy into other forms is the reverse process of Photosynthesis. 

The correct response is potential energy. This is stored energy at rest. It's energy waiting to be used. However, if the car was moving they would would call it kinetic energy - energy in motion. Since in the questions the car hadn't been started yet, kinetic energy is the incorrect response. Radiant energy is from the sunlight, thus that answer is incorrect. Metabolic energy is related to digestion so that response is incorrect.

The correct response is natural gas. This is an example of a fossil fuel - like coal and oil. Fossil fuels are considered non-renewable resources because once they are used up, they are gone forever. All of the other answer choices are considered renewable resources because they can be used multiple times without being depleted. For example, if an individual adds solar panels to their home, then they will receive energy day after day - sunlight is not completely used up by the solar panels.

A kilowatt-hour is a unit of energy equal to one thousand watt-hours. A watt-hour is the amount of energy used to power a hypothetical device for one hour that requires one watt of energy to function. Thus, a kilowatt-hour is used to measure energy consumption.

The second law of thermodynamics states that when energy is converted from one form to another, some energy is lost and efficiency decreases. The energy from gasoline igniting is lost to friction from the engine and converting energy in the form of a combustion to the form of wheels rotating forward. Efficiency of energy use is lost in this conversion process.