"Enigma" means puzzle or something difficult to understand. "Accreditation" means providing credit or approval for an institution (usually a school). "Zealot" is a person who is passionate for something. "Fatigue" means exhausted and worn-out. "Herbivore" is an organism that eats only plants.

"Felicity" means bliss or extreme happiness. "Inconsistent" means not constant or not the same throughout. "Frightful" means horrible or causing fear in people. "Humid" means that there is a lot of moisture in the air. "Inactive" means not moving or not involved with physical activity.

The word “alacrity” is related to the musical words “allegro” and “allegretto,” which indicate quickness or briskness of tempo. Strictly speaking, “alacrity” means pleasant, quick readiness (to do something). Among the provided options, the best answer is “willingness.”

"Zenith" means apex or highest point, so "apex" is the correct answer. None of the other answer choices are close in meaning to highest point: "zealot" means fanatic or enthusiast; "reconciliation" means agreement or harmony reached after an argument or battle; "cessation" means ending or conclusion; and "vulgarity" means crassness or obscenity.

"Mettle" is a noun that means "courage; fortitude" or "the ability to cope well with difficulties; resilience." While "diffidence" might seem like a promising answer choice, it actually means "modesty or shyness resulting from a lack of self-confidence," so it's an antonym of "mettle," not a synonym. "Dauntlessness," on the other hand, means "fearlessness, intrepidness, boldness; the incapability of being discouraged or intimidated" and is the best answer choice of those listed.

"Harbinger" means something that signals the approach of a person. "Vegetation" refers to plants or crops. "Proposal" means plan or a suggestion. "Tactic" is a strategy or plan. "Probability" means the chance or likelihood of something occuring.

Contempt means “feeling that something or someone has no worth or deserves no respect.” For example, one could say, “Thomas showed contempt for all of his neighbors, for he thought they were leeches on society, providing nothing for the common good or even for themselves.” The word “disdain” is related to “dignity,” but the “dis-” prefix implies the opposite of root that is related to dignity. Therefore, expressions of “disdain” are the opposite of expressions of worth.

"Windfall' is a noun that is defined as "an unexpected, unearned, or sudden gain or advantage" or "a piece of unexpected good fortune, typically one that involves receiving a large amount of money." While "trip" may sound like a potentially correct answer because "windfall" is created from a combination of the words "wind" and "fall," "windfall" does not mean "to knock something over with wind" or have anything to do with falling, so neither "blow over" nor "trip" can be the correct answer. "Jackpot," a noun meaning "a large cash prize in a game or lottery, esp. one that accumulates until it is won," is the closest synonym to "windfall" amongst the listed answer choices, so it is the correct answer.

Since "apex" is a noun that means "the top or highest part of something, especially one forming a point," we need to pick out another noun that means "top." While "foremost" means "most prominent in rank, importance, or position," it is an adjective, and not a noun - it describes something at the top, not the top itself, so it can't be the right answer. "Pinnacle," however, means "a high, pointed piece of rock" or "the most successful point; the culmination," and since it is closest in meaning to "apex," it is the right answer.

Eminence often refers to royalty, and means dominance or superiority—in this case, "prestige," which also means superiority or power, is the best synonym.