The most frequent use of "corroborate" is probably in the sense of a courtroom testimony "corroborating" the truth or falsity of some claim. Such corroboration helps to support the claim being made. Such evidence is the opposite of contradicting evident—i.e. evidence that seems to speak against the claim being made.

We often speak of divulging in the context of secrets that are divulged. This means that they were revealed. Surprisingly the word is related to "vulgar" which means the masses or the common people. When you divulge something, you tell it to everyone—even the "commoners." In contrast to this, when we conceal something, we "cover it up" or keep it from being known or seen.

The word "accost" does not have to do with the price of goods. Strangely enough, it comes from the Latin that literally means to be at the side of someone or something else. In English, it means to speak to in a strong and vigorous manner. Often, it is an aggressive kind of speech, confrontational in nature. The point for this question is that accosting is directly addressing something. In contrast to this, evading something is avoiding it, quite the opposite of dealing with something "head on."

The word "alleviate" comes from Latin roots meaning light (in the sense of being not heavy). To alleviate something is to make it lighter or to reduce it. Related words are "levity" (meaning humor or light-heartedness) and "levitate." The best contrast among the options given is "exacerbate," meaning to make worse. It is related to "acerbic," which means biting and sharp—as in "acerbic wit."

The word "substantial" can mean that something is not ideal but instead is real and tangible. (Something "tangible" can be touched. This is related to the word "tactile.") In contrast to something substantial, the word "intangible"—not touchable—is an excellent antonym.

When something is "opaque," that thing prevents light from passing through it. For example, a house wall is opaque to the light in a given room, preventing it from passing into the next room. In contrast to this, the windows in the room are "translucent," meaning that they allow light through them. This word comes from the combination of the prefix "trans-," meaning across, and "lucent," which comes from light. Translucent surfaces literally allow light to shine through or across them.

"Placid" is an adjective that can mean calm; not easily excited when talking about a living organism. It can also mean calm when describing water. When taking a test, if there is more than one meaning for a word, it is best to look at all of the possible answers and eliminate the ones that don't fit any definition.

Using this strategy, we can eliminate "tranquil," because it means peaceful. This is a synonym of "placid," not an antonym.

"Perplexed" can also be eliminated because it means confused. This is not the opposite of "calm."

"Innocent" means harmless and free of guilt. Again, this is not the opposite of calm.

This leaves us with two possibilities: "excitable" and "aggravating." "Excitable" is an adjective meaning easily excited. "Aggravating" is an adjective meaning irritating. "Excitable" is the best antonym for the first definition of "placid."

Most of the wrong answers are trying to make you think that the "ver-" at the beginning of "veracious" is the same as "very." However, this comes from the Latin for truth. Someone is called "veracious" when he or she is truthful. (Likewise, words are called "veracious" when they are truthful.) The best contrast to this is "deceitful," which is quite opposed to being truthful.

When something is authentic, it is accepted as being genuine—not judged as being a fake version of something. Sometimes, people will speak of a person as being "authentic," implying that he or she is not fake in his or her self-presentation; however, for this question, the general sense is "authentic" as genuine. A forgery is far from being a genuine version—it is a faked version meant to trick people. (Think of a forged signature.)

The word "nascent" comes from roots similar to those of "natal" and "nativity." These words all have to do with birth or coming to birth. Here, the sense is of something that is coming into existence—a nascent idea or a nascent personality trait (or something else of the like). In contrast to this, something dying is ending its time of existence and development.