"Tacit" means implicit or understood.

"Plausible" means believable or potentially true, so "believable" is the correct answer.

"Apocryphal" means seemingly true, but actually false. None of the other answers are close in meaning to "apocryphal": "interesting" means holding one's attention or fascinating; "scared" means afraid; "tainted" means adulterated; and "indecent" means not decent or obscene, as one might infer from from the presence of the negative prefix in- in the word.

"Tenable" means reasonable or able to be defended. None of the other answer choices are close in meaning to "tenable": "sickly" means looking as if one is ill; "forged" means not authentic; "inventive" means creative; and "dusty" means covered in dust.

"Ineffable" and "inexpressible" both mean unable to be put into words, so "inexpressible" is the correct answer. None of the other answers are close in meaning to "ineffable": "defamed" means slandered; "prayerful" means characterized by prayer; "shaded" means in an area of comparative darkness; and "stolen" means taken without permission.  

"Flagrant" means obvious or unconcealed, so "obvious" is the correct answer. "Hidden" is an antonym of "flagrant"; it means not obvious or concealed. "Knowledgable" means knowing a large amount of information about a certain subject or smart. "Flimsy" means fragile or easily broken. "Exuberant" means excited or lively.

"Doubtful" means hesitant, unsure, or not likely true, so "uncertain," an adjective that means hesitant or unsure, is the correct answer. None of the other answer choices are close in meaning to "doubtful" and "uncertain": "affable" means friendly and easy to get along with; "pleasant" means providing joy or happiness; "considerate" means kind and thoughtful; and "proper" means suitable or correct.

"Absurd" means unreasonable or ridiculous. "Amiable" means friendly. "Shocked" means to be surprised. "Detached" means not connected or unconcerned. "Vague" means not clear or hard to understand.

The word "understood" means implied but not stated. "Tacit" is the best answer choice because it has a similar definition: understood without being openly expressed. Considering the other choices, "confound" means to surprise or confuse, "purport" means to profess or claim, "relay" means to deliver (as in "to relay a message"), and "adjunct" means something that is added to something else but is unessential.

"Blatant" is an adjective meaning done in a shameless manner when referring to bad behavior, and overt and obvious in other instances. So, we need to pick out an answer choice that means something like obvious. Since "patent" can mean obvious when used as an adjective, "patent" is the answer choice closest in meaning to "blatant" and the correct answer.