Generally speaking, we use the word "pious" to refer to someone who is religious in a devoted way. In the past, the word used to deal with someone's respect for his or her parents, though this use is much rarer today. Sometimes, "pious" is used to describe someone who is showy with his or her religiousness, though is actually quite nasty and immoral. In this question, however, the only acceptable option is "devout."

Whenever something "wavers," it sways from side to side. If "waver" when you walk, you don't walk a linear path, but instead move from side to side as you proceed forward, winding back and forth.

Whenever we describe someone as being "unwavering," we are saying that he or she is unchanging. This person does not go off the side of the path that has been chosen. Such a person is devoted to what he or she is doing. Hence, "steadfast" is an excellent synonym. It means standing steadily in the sense of meaning unchanging and devoted.

Likely, you know the word "aggressive" in some manner. An "aggressive" person is pushy and generally pretty combative. He or she really does a lot to get his or her way. Aggressive people are not much fun to be around (at least most of the time). So, it's tempting to say that the word means "angry," "enraged," or even "antisocial"; however, being aggressive primarily has to do with being pushy or, as is appropriate given our options for this question, "assertive."

The word "humane" is related to the word "human." In a way, it means acting in a way that befits a true and good human person. Thus, a "humane" person is someone who is understanding and compassionate, not mean and rude. The only option that expresses this general meaning is "understanding." A number of the other options try to trick you by getting you to pick a word that hints at the fact that human beings are very developed creatures. Do not be tricked by these!

The definition of "innate" is possessed at birth or a natural trait. Therefore, the sentence provides the necessary clue for the missing word where it states "babies do not need formal training." The other answer choices do not match this definition.

"Frugal" means "thrifty" or economical. The other answer choices here do not relate to money or other expenses.

Whenever someone is "gullible," he or she will believe just about anything whatsoever. You can easily "use" or exploit a person who is like this. That is, a gullible person can be tricked for you to gain an advantage over him or her (if you wanted to, at least).  A more standard synonym for "gullible" is "naive," though this is not an option among those provided.

“Exquisite” means ornate, dainty, and beautiful, so "lovely" is the correct answer. As for the other answer choices, “candid” means blunt and honest; “magnetic” means attractive; “foreboding” means suggesting something bad will happen soon in the future; and "expensive" means financially costly.

“Imminent” means occurring soon, making "looming" the best answer choice. As for the other answer choices, "lavish" means luxurious; "incipient" means just having begun or developing; "fortunate" means lucky; and "gracious" means thankful and polite.

"Toxic" is an adjective that means "causing or capable of causing death or illness if taken into the body" when used of a plant or substance, "producing poison as a means of attacking enemies or prey" when describing an animal or insect, or "extremely unpleasant or malicious." While "fulsome" might look like a good answer choice, "fulsome" actually means "complimentary or flattering to an excessive degree" or "of large size or quantity; generous or abundant," so it cannot be the correct answer. "Poisonous" however, is a synonym of "toxic," so "poisonous" is the correct answer.