"Sympathetic" and "compassionate" are synonyms, just as "insensitive" and "cruel" have similar meanings. 

Something that is “tepid” is lukewarm. The word can be used to describe barely warm water as well as a personality or action that is not very enthusiastic. The first part of the analogy can be read as, “As being barely hot is to something extremely hot.” The second half of the analogy is best matched by the word “freezing,” for this is a greater degree of the coolness implied in “chilled.” Thus, the whole analogy would run, “As something blazing is hotter to a greater degree than something tepid, so too is something freezing cooler to a greater degree than something chilled.”

When someone is attentive, he or she pays heed to the details of a situation, not allowing them to be overlooked or ignored. Quite to the contrary, being preoccupied means that a person is concerned with other things and is not “mentally present.” For instance, you might say, “Sam was preoccupied with his worries about losing his job and thus completely missed the fact that the light had changed from red to green.” The words “attentive” and “preoccupied” are thus relatively antonyms to each other. The word “overjoyed” is obviously an antonym of “miserable,” the only word that even remotely functions as an opposite to being joyous.

The word “gregarious” comes from the word for “a flock” in Latin. The word “congregation” literally means “a gathering together of the flock.” (It is in part for this reason, among others, that all of these varied forms of “flock” language are used by Christians). The word “gregarious” means “friendly” or sociable, as though to say, “able to get along with the flock.” Thus, the words “gregarious” and “unfriendly” are antonyms. Among the options provided for such a contrast with “ready,” only “unprepared” fits this use. All of the others are either wholly unrelated (“agreeable” and “accepting”) or synonymous (“equipped” and, perhaps, “instructued”).

When someone is irritated, he or she is angry or annoyed. This is a state of mind quite different from being calm, so the two words can fairly be called antonyms. The word “liberal” has many uses, but knowing that we need an antonym helps in this question. While “political” really is just a trap answer, the options “accepting,” “tolerant,” and “enlightened” all are legitimate meanings for “liberal;” however, they are also synonyms—which we do not need! Instead, there is another meaning for liberal which is similar to the others but not quite equivalent, namely, to be generous with money / goods. When someone is a miser, he or she is very cheap, trying to spend money whenever possible. This is a good antonym for “liberal.”

When someone is weary, he or she is tired and lacking energy; therefore, “weary” and “energetic” are antonyms. In looking for an antonym for “plain,” the best option is “ostentatious,” which means “showy” (often with the negative connotation that the showiness is done in order to attract attention). This is an adequate antonym for “plain.”

We often think of “aggravate” in the sense of “to make someone angry,” as when we say, “The younger sister loved to aggravate her older sibling by burning his toys in the fireplace;” however, the more general meaning for aggravate is “to make (a condition, problem, wound, etc) worse.” Thus, “relieve” is an antonym to “aggravate,” for relief makes a situation better. Among the answers, only “empty” is an adequate antonym for “fill.” All of the others are either synonyms or not related at all.

The “zenith” of something is its highest point. For instance, one could say, “After World War II, the United States was perhaps at the zenith of its power, having the most powerful military in the world as well as being greatly respected by all of western Europe.” The term “zenith” can mean “top” or “highest point” in a more physical sense as well. Thus, in comparison with the “zenith,” the “bottom” is an antonym. Among the options provided, mediocrity is the only antonym for excellence. When something is “mediocre,” it is only of “middling” or average quality. This is usually used to imply that it is not very good at all—“just average” in the somewhat negative sense of the expression.

The “nadir” of something is its lowest point, as when one says, “After being fired from his job, evicted from his apartment, and abandoned by all his friends, Egbert was sure he had reached the absolute nadir of his life.” This is an antonym to “summit,” which means “the highest point;” therefore, you need to look for an antonym for “victory.” Although it is a rather simple word, “defeat” works very well and is the best choice among those provided. The others are either synonyms or not related in any meaningful manner.

When something is adequate, it fulfills a given need. For instance, someone can say, “Although it was not perfect, the insulated jacket provided adequate protection from the brutal cold, ensuring the survival of its wearer.” This is quite the opposite of “insufficient,” which is used to describe things that do not fill a given role in an adequate manner. One could speak of a house having “insufficient insulation” if the insulation was too thin to provide protection from the winter weather. Thus, we are looking for an antonym. The best antonym for “ill” is “healthy.” “Sickly” and “ailing” are synonyms. The others are not related in any relevant manner.