The contrast in this sentence is between possible and impossible tasks. It is not necessarily about easy and difficult tasks (though impossible tasks are supremely difficult). Thus, we can eliminate the tempting wrong answers "facile" and "simplistic." The word "feasible" means possible. It can indicate that something is easy, but it means more broadly able to be done. This is its main meaning. Thus, it is the best option among those provided.

There are several clues that will help you determine this sentence's answer. First, the first classes are contrasted with advanced classes, which treated more "difficult matters." Also, the second sentence states that professors must start with "understandable" texts. Thus, the blank likely means not understandable. The point is that a first class cannot use difficult and not-understandable texts. Something that is "impenetrable" is very difficult to understand. It is like the mind cannot penetrate through to the meaning.

The sentence focuses on the fact that Sean had undertaken work that was straining (difficult) and "concentrated." Thus, while his work may well have been "technical," "intelligent," and even wise ("sagacious"), it is best to say that he had been looking through the scope "intently." This means that he had focused attention on the task—something that is very straining and concentrated.

Several clues will help you with this sentence. First, we can guess that Mary had requested help for some time. John had "long ignored" her requests. Likewise, we can tell that his patience was broken down by her "inquiries." Now, we can't say whether or not they were abusive inquiries, but it is appropriate to say that they were "long lasting"—she kept asking for a long time, eventually making him lose his patience enough to agree to give her the assistance. Something that "persists" lasts for a long time, no matter what hardships come its way. The trait of being "persistent" describes something that lasts a long time in this manner. This is a good way to describe Mary's inquiries, given the clues in this sentence.

The only clue that you are given in this sentence is that some bacteria have become "able to withstand" drugs. From this, you cannot say that the bacteria has necessarily become more fatal or life-threatening ("deadly"). Even though it is resistant, you cannot guarantee that it is more dangerous. (It likely is, but you cannot go beyond what is directly stated or implied in the sentence.) The word "resilient" means able to withstand difficulties. These forms of bacteria are "resilient" in that they are not as easily killed by drugs.

If you read the sentence directly, the meaning is rather direct. It implies that some people "find a large number of options to be" overwhelming—hence, they cannot make any choices when presented with so many options. When something is "bewildering," it makes someone feel confused. If someone is confused by many options, it would be quite difficult for him or her to make a choice regarding them.

The key characteristic by which Mark is described here is his readiness to "help" his friends. This describes a person who is loyal and generous. Now, you likely know that "vivacious" and "precocious" mean something positive, but "vivacious" means lively and "precocious" means very advanced for a young age. Neither of these are appropriate. "Orderly" and "exalted" do not make sense here, either, for they do not express the idea of loyalty (though "orderly" might make you think this, given that "orderly" things exhibit a kind of regularity). Thus, the best option among those provided is "devoted," which explicitly means loyal.

The key clue in this sentence is "that he believed had been lawfully elected." This describes the kind of authority that Francis believed to be acceptable. When something is done according to the law or lawfully, it is "legitimate." The word actually comes from the Latin "legis," meaning "of the law." This is the best option among those provided, for it alone implies this kind of legality.

The key thing to note in this sentence is that the teacher in question lacks experience. Thus, we cannot say anything about his age—whether he is old or young remains unstated. Although it is usually used as a noun, the word "novice" can be used as an adjective to describe someone who is inexperienced. Thus, this teacher is best called a "novice teacher" because he is said to lack experience. The word "novice" comes from the Latin "novus," meaning new. We see this word in other English words like "novel" (an adjective describing something new) and "nova" in "supernova," which describes a kind of new brightness in the sky when a star explodes.

Now, it is likely that you will think that the sentence is describing Richard's lack of sleep as being "exhausting" or even "demanding;" however, the sentence really is not addressing this aspect of his lack of sleep. Instead, it is concerned to say that it was indeed a harm to his health, even though he did not think it would be. Thus, the best option is "detrimental," meaning harmful.