“Extinct” means wiped out, died out, no longer around. As in, the dinosaurs are “extinct.”

Believeable and authentic relate to being convincing or likely. 

"Candid" is an adjective meaning truthful and holding no information back, so we need to pick out another adjective that means something like truthful. Since "honest" means sincere or virtuous, "honest" is the answer choice closest in meaning to "candid," so "honest" is the correct answer.

Someone who is "oblivious" is not aware of what is going on, so the correct answer is “unaware,” a word that means not aware, as you may have inferred from the word's use of the negative prefix "un-," which means not. None of the other answer choices are close in meaning to "oblivious": "susceptible" means vulnerable or in danger; "unusual" means not normal or weird; and "creative" means imaginative.

Something that is "authentic" is genuine and real, so "real" is the correct answer. "Authentic" is an opposite, or antonym, of "fake," which means not genuine. To help you, "disparate" means different, "distinct" means easily recognizable due to differences from something or someone else, and "commonplace" means ordinary.

"Frank" means addressing the truth directly regardless of people's feelings, so the best synonym is "straightforward," which means simple when referring to actions or direct and honest when referring to people. As for the other answer choices, "friendly" means amiable, "fair" means just or treating everyone equally, "sympathetic" means identifying with on an emotional level, and "untrue" means false.

"Blunt" means expressing things clearly and honestly, which is also the definition of “straightforward.” So, "straightforward" is the correct answer. None of the other answer choices are close in meaning to "blunt": "stubborn" means not changing one's mind or plan even when urged to; "calculating" means cunning; "sympathetic" means thinking about other people’s feelings, and "silent" means making no noise.

“Authentic” means real or genuine. To provide further help, “phony” means the same thing as “fake," and “unsuccessful” means not completed or failed.

“Straightforward” can mean honest when used to describe a person, or simple and easily accomplished when used to describe a task. To provide further help, “deceitful” means dishonest; “comely” means cute; “savage” means wild and vicious; and “furious” means very angry.

“Legitimate” is a word that can be used as an adjective or as a verb, but because all of the answer choices are adjectives, that means that we will need to consider “legitimate” as an adjective. When used as an adjective, “legitimate” can mean “conforming to the law or to rules” or “able to be defended with logic or justification,” so we need to pick out an answer choice that means something like “legal,” “logical,” or “justifiable.” That means that “doubtful” cannot be the correct answer, because “doubtful” is an adjective that can mean “not established as genuine or acceptable,” making it an antonym, not a synonym, of “legitimate.” “Valid,” however, is adjective that can mean “having a sound basis in logic or fact; reasonable or cogent,” when used of an argument or a point, or “legally and officially acceptable.” “Valid” is the answer choice closest in meaning to “legitimate,” so “valid” is the correct answer.