"Prudent" means sensible or careful, so "sensible" is the correct answer. For clarification, "deleterious" means harmful, "fundamental" means basic or important, "insignificant" means not important, and "efficient" means organized and productive.

"Staid" means grave and serious, so "serious" is the correct answer. For clarification, "incumbent" means in office or currently serving, "inferior" means of worse quality or not as good, "deranged" means crazy or out of one's mind, and "formless" means amorphous.

"Miserly" means not generous of spirit and as such is most similar in meaning to "parsimonious," a word which means stingy. So, "parsimonious" is the correct answer. For clarification, "ostentatious" means showy and pretentious, "worldly" means mature, sophisticated and wise or concerning material things as opposed to spiritual things, "generous" means liberal or openhanded, and "knowledgable" means knowing a lot about a particular subject.

"Tenacious" means stubborn, inflexible, or relentless and as such is most similar in meaning to "obstinate," a word which means stubborn or refusing to change. So, "obstinate" is the correct answer. For clarification, "lampoon" is a verb which means mock, "supreme" means ultimate, dominant, or best, "grand" means magnificent or main, and "forgiving" means merciful or lenient.

"Zealous" means passionate, so "passionate" is the correct answer. For clarification, "whimsical" means silly or quirky, "loquacious" means talkative, "basic" means fundamental, and "quixotic" means unrealistically idealistic.

"Keen" means either eager or sharp-witted. So, "sharp-witted" is the correct answer. For clarification, "banished" means sent away, and is an antonym of "welcomed," which means amiably received. "Ill-tempered" means crabby or cranky, and "jocular" means jovial, playful, or funny.

"Mercurial" means unpredictable, capricious, or mysterious, so "unpredictable" is the correct answer. For clarification, "fey" means supernatural, "notorious" means infamous, "profane" means rude and disrespectful or worldly as opposed to spiritual, and "magical" means of or related to magic or extraordinary.

"Ostentatious" means showy or pretentious, so "showy" is the correct answer. For clarification, "parsimonious" means stingy or not generous, "destitute" means very poor or having no possessions, "abstinent" means refraining from doing something, and "messy" means unorganized or dirty.

Someone who is "astute" is smart, shrewd and quick-witted, so "shrewd," a word that means clever, is the correct answer. For clarification, "imprudent" means not prudent or rash, as you might be able to infer from the word being a combination of the root "im-," which means not, and "prudent." "Daft" and "harebrained" can each mean absurd or foolish, and "thoughtless," as you might guess, means done without thinking, and specifically done without thinking about the emotions of others, or in other words, inconsiderate. 

Someone who is "imperious" is very arrogant and self-assured, so "arrogant" is the correct answer. For clarification, "pious" means deeply religious, and "sanctimonious" means self-righteous or smug.