Among humans, peers are people who are "equal." To be "peerless" means to be without anyone or anything that is your equal. A "peerless diamond" is one that is of such quality or beauty that it cannot be matched by another. Therefore, the word "peerless" means unrivaled. A convention is a generally held belief or practice, and something that is "conventional" is done in accord with such general beliefs or practices. Such things are very ordinary and repeatable. This is quite different from something that we would call "peerless."

The adjective "scant" means of little amount to the point of being insufficient. To give "scant attention" to something is to pay very little attention to it, and to say something is "a scant three gallons" means that it is barely three gallons. In contrast to being barely enough, an excellent antonym is "abundant", meaning plentiful.

The word "negligible" is related to the word "neglect." We tend to neglect something that is not very important to us. Something "negligible" is very small and insignificant. In contrast to this, something "significant" is important. A "significant amount of time" is a good deal of time, and a "significant event" is one that is important.

The word "senescent" is related to roots from which we get words like "senior" and "senator," the latter really describing a person who is supposed to be old and wise. To be "senescent" is to be aged, often with the effects of deterioration that come with the passage of time. Although the word "adolescent" can be a bit negative, it does not have to be such. It can merely mean that someone is in the period of youth in which he or she is passing to adulthood. Among the options provided, this is the best temporal contrast to "senescent."

When someone "plods along," he or she moves at a slow speed, often as though he or she has a heavy burden on his or her back. Do not be tempted to pick an answer like "joyous." Just because someone is plodding, he or she does not necessarily do this because of being depressed or sad. The best antonym is "expeditious," meaning done quickly and efficiently. To "expedite" a process is to make it happen more quickly.

The word "inanimate" comes from the Latin root meaning to have a soul. We generally refer to things as being "animated" when they move, seeming to have self-motion. An "animate" being is one that is living. The most tempting wrong answer given for this question is "biotic," which means relating to living things; however, this does not describe the living thing itself. The best answer—as homely as it might seem—is "living."

The word "precipitate" is most often associated with the phenomenon of meteorological precipitation—as when it rains or snows. This is a specific case of the more general process of something falling out of solution or suspension. We can say that a person makes a "precipitate decision" when he or she makes a quick and unmeasured decision—proceeding as quickly as the dry skies begin to fill with rain. Thus, such a hasty decision is well contrasted one that is thought out and measured—i.e. to a prudent decision.

Something that is protracted is drawn out or lasting for too long of a time. Do not associate this word with the mathematical/geometrical options given in the question—all of these are trying to get you to make a false association. In contrast to being "protracted," "brief" is an excellent antonym. A "protracted affair" is one that is too long, but one that is brief is quite short in contrast.

Several of the wrong answers attempt to have you associate "brilliant" with the sense of being intelligent—a standard and acceptable usage. However, none of these wrong options are well enough matched as antonyms—they would have to be explicitly opposed to such intellectual ability. Instead, "brilliant" is being used here in a more literal and physical sense—describing something that is bright in the light. Something can be physically "obscure" when it is shadowed or darkened. (From this, we talk about an "obscure idea," which is perhaps the more standard use of the word "obscure" in our day-to-day talk.)

The word "copious" comes from the Latin for store or plenty. When something is "copious," it exists in great quantities. The best antonym is "meager," meaning little in quantity or quality.