"Bitter" and "sweet" are antonyms, just as "pungent" and "mild" have opposite meanings.

When something is "ruffled", it is literally taken out of order or arrangement. We often speak of "ruffling" someone's hair or some other semi-arranged set of items. As an emotional state, "ruffled" means disturbed or not calm. In contrast to this, the term "placid" means calm with little disturbance or change.

The word "brisk" can refer to cool weather, but it can also be used as an adjective describing fast movement. The adverb "briskly" means quickly or with energy. A brisk motion is one that is fast, and walking briskly means walking quickly with haste. In contrast to this, a leisurely pace is one that is slow—taking its time. Leisure is the free time used for enjoyable activities. Such time is not usually stressful. Therefore, "leisurely" activities are quite slow in their pace.

Clearly the words deny and affirm are opposites. When we deny an accusation, we refuse to admit that it is true at all. In contrast, an affirmation is a statement that something is indeed the case. Thus, the analogy is one of antonyms. The opposite of “accept” is “reject.” Though a rather simple answer, it is still the best option.

The word “potable” comes from the Latin word for “to drink” or “drinkable.” This latter sense still is retained in the English, as the word “potable” means either “drinkable” or “safe to drink.” When liquid is potable, it is free of any contamination. Thus, the analogy could be written, “As potable water lacks contaminants, so does something that is healthy lack X.” Among the options provided, only “disease” fits the needed sense of that which is lacking in someone who is healthy.

"Advance" is the opposite of "retreat," so therefore the opposite of "ascend" would be "descend," or to go down.

When someone "plods along," he or she moves at a slow speed, often as though he or she has a heavy burden on his or her back. Do not be tempted to pick an answer like "joyous." Just because someone is plodding, he or she does not necessarily do this because of being depressed or sad. The best antonym is "expeditious," meaning done quickly and efficiently. To "expedite" a process is to make it happen more quickly.

We are looking for something that simply implies irregularity as opposed to regularity. When something is done inconsistently, it is done without a regular manner or mode. A consistent tempo is one that is regular and repeated. Therefore, "inconsistently" is a good antonym for "regularly."

To exasperate someone is to make that person completely tired and irritated about something. For instance, "The arduous and tedious process of reviewing the details of the exam exasperated the young man, for he knew all of the answers already." An exasperated person is likely quite angry, so "delighted" is an excellent antonym for this word.

We tend to think of "vulgar" in the sense of "vulgarity" or the use of swear words; however, this notion comes from the general notion or meaning of "vulgar," which comes from the Latin meaning pertaining to the ordinary people. Something vulgar is lacking in refinement or culture. Therefore, the best antonym among the options provided is "refined," meaning elegant or cultured.