"Marginal" is an adjective that can besides meaning "of, relating to, or situated at the edge or margin of something," can also mean " of secondary or minor importance; not central." So, we need to pick out an adjective that means something like "of minor importance." Neither "crucial" nor "monumental" can be the correct answer, then, because each word is an antonym of "marginal," not a synonym. "Negligible," however, is an adjective that means "so small or unimportant as to be not worth considering; insignificant," and because it is the answer choir that is closest in meaning to "marginal," "negligible" is the correct answer.

"Innocuous" is an adjective meaning innocent and harmless. For example: "The innocuous bull snake is often mistaken for the deadly rattlesnake."

"Invariably" is an adverb meaning always.

"Conglomerate" is a noun meaning distinct items that can be put together make a whole with distinct parts. A space station might be an example of a conglomerate.

"Vaccine" is a noun meaning a substance that makes the antibodies which inoculates a person against disease.

"Indicate" is a verb which means to point out or to show.

"Harmless" is an adjective which means innocent and inoffensive. Harmless has the most similar meaning to "innocuous."

When someone is "infuriated", he or she is extremely angry. The word "irate" comes from the Latin root meaning anger. It is related to the word "ire" (anger) and "irritated." Although its Latin roots mean merely "anger," in English, the word "irate" means greatly angered. Therefore, it is a better option than merely saying "angry."

The word "ecstatic" comes from the Latin root meaning to stand. We see this in words like "stationary" and even "static." A static signal on a radio is one that is merely sound that stays the same—not changing as does a real voice or other organized sound. The word "ecstatic" has the prefix "ex-" on the front of it (though it has become "ec-").  This means outside of or out—as in "exit." Someone who is ecstatic is so overjoyed that he or she is "outside of himself or herself." We sometimes say that such a person is "beside himself or herself." The word "enraptured" means something similar to this, and it is related to the word "capture"—as though someone were so overwhelmed by something (beauty, joy, etc.) as to be "captured" or "snatched up."

"Forlorn" means miserable or sad. "Ecstatic" is the antonym; it means extremely happy. "Arrogant" means conceited or full of oneself. "Informed" means having knowledge or information regarding a topic. "Significant" means important or noteworthy.

"Abject" means downtrodden and hopeless, so "downtrodden" is the correct answer. As for the other answer choices, none are close in meaning to "abject": "ambiguous" means having more than one meaning; "audacious" means brazen or bold; "diffident" means hesitant or lacking in confidence; and "laudable" means admirable or praiseworthy.

"Incensed" is an adjective that means "very angry; enraged," so we will need to pick out an adjective that means something like "very angry." "Serene" cannot be the correct answer, then, because "serene" is an adjective that means "calm, peaceful, and untroubled; tranquil," making "serene" an antonym, not a synonym, of "incensed." "Furious," however, is an adjective that means "extremely angry" or "full of anger or energy; violent or intense," and because "furious" is the answer choice closest in meaning to "incensed," "furious" is the correct answer.

Someone who is affable is pleasant and friendly.  For instance, an affable friend is warm and kindhearted.

“Morose” means in a bad mood and miserable, so "sulky" is the correct answer. “Lofty” means high-up or proud; “timid” means shy and quiet; “tepid” means lukewarm when describing temperature and unenthusiastic when describing responses; and "macabre" means morbid and grotesque.

“Jovial” means jolly, friendly and "cheerful." As for the other answer choices, “uncomfortable” means slightly painful or just removing or lacking all comfort; “hollow” means containing empty space on the inside; "nuanced" means full of subtle details; and “deft” means skillful.