"Incisive" (usually used to describe people or thought processes) means acute, sharp, or cutting. "Chronically" means persistently. "Vacant" means empty. "Vigilant" means alert and watchful. "Frivolous" means carefree, flighty, and flippant.

"Tantamount" is an adjective that means "equal in seriousness to; virtually the same as," so we need to pick out another word that means "equal." While "indifferent" may look like a good answer choice because it looks like "in-" ("not") and "different," "indifferent" actually doesn't mean "not different," but instead means "having no particular interest or sympathy; unconcerned," or "neither good nor bad; mediocre," so it's not the word we're looking for. "Equivalent," however, means "equal in value, amount, function, or meaning," and because it is the answer choice closest in meaning to "tantamount," it is the correct answer.

“Nefarious” means wicked, infamous or evil. For clarification, "unscrupulous" means not restrained by moral or ethical principles; "discerning" means selective and showing good judgment.

"Crepuscular" describes the "twilight" or dusk. "Dulcet" means sweet-sounding or mellifluous. "Ordinary" means average or normal. "Burnished" means polished or shined by careful rubbing, and "rotund" is a synonym for "plump."

"Exorbitant" means excessive or prohibitively high. "Gorgeous" means very beautiful, and "largely" means mostly or mainly. "Gregarious" describes someone who is outgoing, while "garrulous" describes someone who is talkative.

"Ecumenical" and "catholic" both mean all-encompassing, universal. (Don't confuse catholic with "Catholic," a specific religious denomination.) "Germane" is an antonym for "irrelevant." "Exuberant" means overjoyed, while "tyrannical" means authoritarian and cruel.

"Censorious" means overly critical. "Academic" describes institutionalized study, usually at a university. "Dulcet" means mellifluous or sweet sounding. "Fatuous" is another word for "silly," and "facile" is a synonym for "simplistic" or superficial.

"Acute" means sharp, or focused. For clarification, inane means absurd or pointless; dignified means composed or noble.

"Magnanimous"means generous or forgiving, especially towards a rival or subordinate.

"Vehemently"means with strong feeling or passion.