"Inquisitive" means "curious," the trait of asking questions or seeking knowledge.

"Petty" means insignificant, trivial or narrow-minded.

"Empathetic" means caring, compassionate, loving.

"Boring" means uninteresting, dull, monotonous.

"Unique" means alone, special, rare.

"Diabolical" means "wicked," devilish or cruel.

"Harmless" means safe, innocuous, or describes something that is not dangerous. 

"Ingenious" means very clever, brilliant or creative.

"Able-bodied" means strapping, strong, or physically fit.

"Benevolent" means kind, good-hearted, generous.

The correct answer is "obedient."

"Docile" is an adjective that means ready to accept instruction; "obedient" is a synonym of "docile" meaning to comply with orders or requests.

"Churlish" means crude, boorish, rude or grumpy.

"Petty" means narrow-minded when describing someone's personality; it can also mean insignificant or trivial or unimportant.

"Gracious" means kind, giving, amiable. 

"Scrupulous" means very careful, meticulous or fussy.

"Refined" means cultured, civilized or elegant.

Lewd means vulgar.

"Tedious" means boring or dull.

"Burgeon" is a verb that means "beginning to grow or increase rapidly, flourishing," or "putting forth young shoots; budding" when used of plants, so we need to pick out another adjective that means something like "flourishing." Since "escalating" means "increase rapidly" or "become or cause to become more intense or serious," "escalating" is the answer choice closest in meaning to "burgeoning," so it is the correct answer.

“Engrossed” is an adjective that means “having all one’s attention or interest absorbed by someone or something.” So, we need to pick out an answer choice that means something like “absorbed.” That means that “bored” cannot be the correct answer, because “bored” is an adjective that means “feeling weary because one is unoccupied or lacks interest in one’s current activity,” making it an antonym, not a synonym, of “engrossed.” “Riveted,” however, is an adjective that can mean “attracted and completely engrossed,” and because “riveted” is the answer choice closest in meaning to “engrossed,” “riveted” is the correct answer.

“Null” is a word that can be used as an adjective, noun, or verb, but because all of the potential answer choices are adjectives, we will need to consider “null” as an adjective. When used as an adjective, “null” means either “having no legal or binding force; invalid” or “having or associated with the value zero.” So, we need to pick out an answer choice that means something like “cancelled” or “associated with the value zero.” That means that “valid” cannot be the correct answer, because “valid” can mean “legally binding due to having been executed in compliance with the law” or “legally or officially acceptable,” making it an antonym, not a synonym, of “null.” “Void,” however, when used as an adjective, means “not valid or legally binding,” and because “void” is the answer choice closest in meaning to “null,” “void” is the correct answer.

“Ingrained” is an adjective that can mean either “firmly fixed or established; difficult to change” when referring to a habit, belief, or attitude, or “deeply embedded and thus difficult to remove” when referring to dirt or a stain. So, we need to pick out an answer choice that means something like “difficult to change” or “deeply embedded.” That means that “transient” cannot be the correct answer, because “transient” means “lasting only for a short time; impermanent,” making it an antonym, not a synonym, of “ingrained.” “Entrenched,” however, is an adjective that is used of an attitude, habit, or belief and means “firmly established and difficult or unlikely to change; ingrained.” Because “entrenched” is the answer choice closest in meaning to “ingrained,” “entrenched” is the correct answer.