The tone of this sentence is somewhat informal, so bear this in mind when making and confirming your choice. The expression "slog on" means to work hard or to work diligently. This second half intends to say that someone should continue to work hard in the hopes that success may indeed be "at hand." To say that something is "on the horizon" means that it is "nearly here." The horizon is the farthest edge of our view, where the sky meets the ground. Therefore, the expression, "on the horizon" means "almost going to appear"—like the sun appearing on the horizon. This fits well with the first half of the sentence.

First of all, do not "overshoot" your details by choosing something like "poison" or "trap." We cannot justify such specificity without other clues. The key thing to note is the adverb "completely." We clearly are being told that the ants must be utterly killed. Now, "outdo" and "assail" just do not work for anything regarding killing—at least in no direct sense. However, "exterminate" is an excellent word. It not only expresses such killing but does so with completeness. A "terminus" is an end of something (just as a "terminal" at the airport is the branching walkway that goes all the way to the end of the possible planes). To "ex-terminate" is to drive something out beyond the boundaries. In English, it generally means "beyond the boundaries of life"—completely killing.

The intensifying adverb “most” requires us to look for the strongest possible option among those given. While “pleasant” and “agreeable” do work in a certain manner, the word “blissful” best fits for this very strong use. “Bliss” is an extreme form of happiness, denoting complete and perfect joy. Though perhaps an overstatement regarding coffee in general, this sentence clearly calls for such a strong usage and not the weaker ones mentioned above.

Clearly, the point in the sentence is that Sally became drunk from the beverages. It is not right to say that she was incapacitated, a word meaning that she would have no capacity for action whatsoever. Instead, all that can be asserted is that she is drunk. Such a state of health is called “inebriation,” from the Latin “ebrius,” meaning “drunk.”

An “arabesque” style painting is one with flowing lines. The word does indeed mean Arab-like (-esque), for it was believed to be derived in the West from Arab styles of art (which under Islamic influence would have lacked pictorial representation). The actual sources for such art are more complex, related to earlier Greek and Roman forms of ornamentation.

The people were brought into an entry room, which could be considered as the “fore-room” to the main meeting area. Such an area is called an “antechamber” because it comes before (=ante) the main chamber or room. The prefix “ante-” can be found in words like “anterior,” “antecedent,” and “antebellum;” (the last meaning before a / the war—often the American Civil War in our usage in the United States).

If two living things live together and (at least in a sense or to a degree) require each other for life, they have a “symbiotic” relationship. (It is possible to use the word merely to mean that they live in close proximity, though general usage often implies the advantageous nature of the relationship). The word comes from Greek roots. “Sym” (or “syn”) means together or “same” and is found in English words like “synonym,” “sympathy,” and “synagogue.” The “-biotic” portion comes from a root word meaning life, found in words like “biology,” “biopsy,” and “biography.”

The word “opus” is directly derived from the Latin word for work, and while its English usage often implies a musical work, it can more broadly indicate any artistic work, particularly one that is very large and involved. The word “opus” in Latin has a forms containing the base “oper-”, found in English words like “opera” and “operate.”

The key expression here is “focusing on every word . . .” This gives the sense of paying close attention to each word in the articles. The word “scrutinize” means to examine or inspect thoroughly, which captures this sense.

In contrast to the other words given as possible answers, being “despondent” implies lack of hope—not merely disappointment or emotional detachment. This is called for by the key phrase, “to the point of no longer hoping for . . .”