"Hackneyed" means trite, unoriginal, or overused.

"Vapid" means dull or flat, so "dull" is the correct answer. None of the other words are close in meaning to "vapid": "fiery" means characterized by fire; "problematic" means difficult; "trusting" means believing; and "edible" means able to be eaten.  

"Atrocious" means wicked or brutal. "Eloquent" means expressive or persuasive in speech. "Belligerent" means aggressive and war-like. "Delightful" means pleasant or enjoyable. "Confidential" means secret and unknown to the public.

"Insipid" means bland or without taste. "Amphibian" is used to describe an animal or item that can exist or can function on land and in water. "Favorable" means approving or advantageous. "Competent" means capable and having the required skills to complete something. "Hasty" means done with speed, but not with thoroughness.

Something that is "marvelous" is amazing or beyong belief. "Astonishing" is the best choice because it means causing surprise or wonder. Considering the other choices, something that is "typical" is common and would not amaze anyone as a result. The other choices have no relation in meaning to "marvelous."

"Exceptional" means outstanding or brilliant, as does the correct answer, "prodigious." None of the other answer choices are close in meaning to "exceptional": "garrulous" means talkative, "pungent" means having a strong smell or taste, "morose" means gloomy, and "reflective" means either reflecting light or thoughtful.

“Banal” means unoriginal and boring, so "unoriginal" is the correct answer. For clarification, "unseemly" means unpleasant or undesirable; "determined" means motivated; "shallow" describes someone who is not thinking or feeling deeply; and "notorious" means infamous.

“Vapid” is an adjective that means “offering nothing that is stimulating or challenging; empty” so we need to pick out an answer choice that means something like “not stimulating or challenging.” That means that “intriguing” cannot be the correct answer, because “intriguing” means “arousing one’s curiosity or interest; fascinating,” making it an antonym, not a synonym, of “vapid.” “Insipid,” however, is an adjective that means either “lacking flavor” or “lacking vigor or interest,” and because “insipid” is the answer choice closest in meaning to “vapid,” “insipid” is the correct answer.

“Prosaic” describes something ordinary or commonplace. You might have thought the correct answer is “rhetorical” because of the relationship between “prose” and “rhetoric,” but “prosaic” is unrelated to “prose.” For clarification, "rhetorical" means relating to the skill of persuasive language, and "diction" means spoken clarity or choice of words.

"Impeccable" means faultless or flawless.