Accelerate means to increase in speed. Quicken means to go faster. Given these definitions, accelerate and quicken are very close in meaning, and therefore synonyms of one another. 

Hoard means to find and keep large amounts of certain types of objects. Collect means to form a grouping of particular items. Thus, given how similar these words are, they are synonyms for one another. 

When you "refine" something, it means that you "improve" it compared to its original condition. This differs from "glorify," which means to raise in status; "regard," which means to see or think of someone in a certain way; and "reward," which means to give compensation for a job well done.

The word "plunge" has a range of meanings, but all of them have to do with falling in one way or another.  When the prices of something plunge, they fall quickly and greatly. When you plunge a knife into a tomato, you press it into ("down into") its surface. Likewise, when you go for a swim and dive into the water, you plunge down into the water.  It is in this sense that the word is being used here, so the best option is "dive," which alone is a good synonym for "plunge."

To “detain” someone or something means to hold him or her in a specific location without letting them leave. It is usually used when someone has done something bad and someone else has to “detain" that person. The word “release” means to let go and is an opposite of “detain.” The word “assess” means to try to understand by considering all of the factors of something. To “result” means to happen as an effect of something.

"Suffocating" refers to the act of preventing another person from breathing, but can also be used figuratively to describe the act of overwhelming another person. Similarly, "smothering" can refer to the physical act of covering another person's airways, or be used figuratively to describe oppressing someone. Given that these words are so similar, they are synonyms. Additionally, both words can be used as either verbs or adjectives.

To "lend" something means to allow another person to use an item for a limited time and then return it to you. To "give" something means to allow someone to become the permanent owner of something you own, for free. "Give" has a different meaning than "lend," so it is not the correct answer. "Loan," however, is similar in meaning to "lend" because it also means to allow another person to have temporary possession of an item.

To "barter" means to exchange one good for another good. To "trade" means to swap one item for another item. Given that these two words have the same meaning, they are synonyms.

The word “damage” means harm when used as a noun, but it can also be used as a verb meaning to harm or to destroy. This means it is closest in meaning to the word “hurt.” As for the other answer choices, the word “support” means to give help to; "free" means set free; "scare" means cause to feel afraid; and "perceive" means notice.

To “clasp” means to grab onto. You might “clasp” something that has been “thrown” at you. The word “sprint” means run fast, and “stumble” means to trip but recover one's balance before falling.