Something that is "covert" is hidden, or more specifically, hidden from the general public. For example, some police officers will walk around public places in a covert manner so that they can more easily find unsuspecting criminals without being identified as police officers. So, "hidden" is the correct answer.

"Salient" means significant or noteworthy. To help you, "irrelevant" means not important and is an antonym of "salient." To further help you, "unstable" means not balanced, mentally unbalanced, prone to experiencing problems of a psychiatric nature, or volatile; circumstantial means accidental or owed to circumstance; and "exquisite" means perfect, divine, or gorgeous.

"Ambiguous" means "vague," or indefinite and undefined.

"Ambiguous" is an adjective that means unclear, open to interpretation, or vague. For example, one might say, "By avoiding specific details, she kept her story rather ambiguous."

"Incontrovertible" is an adjective that means "not able to be denied or disputed," so we need to pick out an answer choice that means something like "undeniable." "Unbelievable," while beginning with a negative prefix like both "incontrovertible" ("in-") and "undeniable" ("un-") do, actually means "not able to be believed; unlikely to be true," so it is an antonym of "incontrovertible" and "undeniable." "Irrefutable," however, is an adjective that means "impossible to deny or disprove," and because "irrefutable" is the answer choice closest in meaning to "incontrovertible," "irrefutable" is the correct answer.

The word "equivocal" means unclear in meaning due to being able to be interpreted in multiple ways. The best choice is "ambiguous," which means having more than one meaning. Something that is ambiguous is unclear because it can have multiple meanings, as is an equivocal statement. Considering the other choices, "equal" means having the same value, "audible" means able to be heard, and "original" means new or the initial one of its kind.

The word "scurrilous" means offensive. The best choice is "offensive," as it is a part of the definition of "scurrilous." Considering the other choices, "scamper" means run about playfully, "gloomy" means saddened, and "clever" means quick-witted.

The word "vituperative" means abusive. So "abusive," a word that means characterized by treating someone badly, is the correct answer. Considering the other choices, "neglected" means not having received a suitable amount of attention, "criticized" means judged harshly by another when describing something, and "disorganized" means careless.

"Paltry" means having little meaning, importance, or worth or very small or meager. "Insignificant" is the only choice that has a definition similar to that of "paltry."