"Quixotic" is an adjective that means "exceedingly idealistic; unrealistic and impractical" and derives from Cervantes's literary character Don Quixote. While "quotidian" may look like a potentially correct answer choice simply because both "quixotic" and "quotidian" begin with "q," "quotidian" means "of or occurring every day," so it cannot be the correct answer. "Idealistic," which means "characterized by idealism; unrealistically aiming for perfection," is the best answer choice because it is closest in meaning to "quixotic."

"Placid" is an adjective meaning either "not easily upset or excited" when used to describe a person or animal and "calm and peaceful, with little movement or activity" when describing a place or stretch of water. "Levelheaded," an adjective that means "calm and sensible," is the answer choice closest in meaning to "placid," so it is the correct answer.

A "morose" person is of a sullen temperament, often negative and depressing to be around. Among the options provided, the only decent synonym is “gloomy.” The words “conventional” and especially “virtuous” might tempt you given that “morose” looks like “moral.” While it actually is distantly related to these other words, do not be tricked so easily!

"Fractious" means "irritable" and quarrelsome.

The word "fatuous" is an adjective that means foolish or lacking wit. "Dull," which can mean lacking wit, shares the same definition and is therefore the best answer choice. Considering the other choices, "bright" in this context is an antonym of "fatuous" since it can mean intelligent. "Portly" means heavy or fat.

A person who is "glib" is smooth-talking, meaning they are able to speak well. The best choice is thus "smooth-talking," since it is part of the definition of "glib." Considering the other choices, "crass" means rude or gross, "dumbfounded" means astonished, "pivotal" means crucial or important, and "portable" means able to be transported easily.

"Combative" is an adjective that means ready to fight. The best choice is "quarrelsome," since it holds a similar meaning of ready to argue. Considering the other choices, "obedient" is an antonym which means complying with authority, "masterful" means skillful, "torrid" means very hot and arid, or passionate when describing a romantic relationship.

“Diligent” means careful, hard-working, and taking care to do something well, so "careful" is the best synonym amongst the answer choices. “Approachable” means friendly and thus easily approached; “demonstrative” means demonstrating something or openly showing feelings or affection; “eloquent” means well-spoken; and “elegant” means having grace, sophistication, and good taste.

“Capricious” means changing in response to the slightest whims, so "changeable" is the correct answer. Being “reliable” is the opposite of being “capricious”; “flexible” means bendable; “humane” means compassionate or treating something like a human should be treated; and "wanton” means random.

“Dissolute” means of poor moral character, depraved and debauched. “Depraved” means lacking moral character or doing sinful or immoral things, so it is the correct answer. “Imperious” means arrogant and controlling; “laudable” means deserving of praise; “meddlesome” means interfering or prone to getting involved in situations in which one is not supposed to; “vulnerable” means able to be hurt or damaged.