"Donate” means to give something to someone for free, usually someone who needs that thing more than you do, so "give" is the correct answer. While "sell" may look like a potentially correct answer, you receive money for a thing when you sell it, whereas you do not receive any money when you donate something.

“Scarce” means rare or only existing in small numbers or quantities. To provide further help, “common” is the opposite of “scarce” and means abundant and often encountered; “thoughtful” describes someone who thinks about other people’s feelings; and “inconsiderate” is the opposite of “thoughtful."

"Retain" means continue to own after a situation which might have taken something away from you, so "keep" is the answer choice closest in meaning to "retain" and the correct answer.

“Observe” means to watch carefully. To provide further help, “conceal” means hide; “reside” means live in a specified location; “concur” means agree with; and “frequent,” when used as a verb, means visit a location regularly.

"Abolish" and "terminate" both refer to ending something and are closest in meaning. The other answer choices are not synonymous with "abolish." "Aerate," for example, means to give something air.

"Assist" means to help someone, making "help" the best synonym of "assist."

Incorrect Answers:

"Ignore" means to intentionally disregard, and is an antonym of "assist."

"Develop" means to grow and become more advanced.

"Protect" means to keep safe from harm.

"Enlist" means to enroll in the armed forces.

“Gruesome” means unpleasant, horrific, or disgusting, so "horrific," which means horrifying and shocking, is the correct answer. To provide further help, "pleasant" means friendly or enjoyable; "mysterious" means not fully understood and difficult to understand; "controlling" means attempting to take charge of situations one has not been put in charge of; and "unruly" means badly behaved and not following rules or directions.

"Plain" is an adjective that means "not decorated or elaborate; simple or ordinary in character." So, we need to pick out an adjective that means something like "simple" or "ordinary." "Ornate," then, cannot be the correct answer, because "ornate" means "made in an intricate shape or decorated with complex patterns," making it an antonym, not a synonym, of "plain." "Unadorned," however, is an adjective that means "not adorned; plain," and because "unadorned" is the answer choice closest in meaning to "plain," "unadorned" is the correct answer.

Gentle and soft both relate to ones having a mild or kind nature.  They also can relate to being careful with ones touch. 

Active and moving both relate to being in motion.