Let's break down the sentence and find the best fit for the blank:

Analyzing the Context:
The sentence begins with "In contrast to instances where size is commensurate with potency of flavor..." This sets up an opposition. "Commensurate with potency of flavor" means that bigger size equals stronger flavor. So, the contrast means that in this instance, smaller peppers don't have a flavor potency commensurate with their size. Instead, they are "far more $\qquad$ than larger peppers."

The key phrase is "potency of flavor," which implies strength or intensity. If smaller peppers are in contrast to being commensurate in size and flavor potency, and considering that peppers are known for their heat, the blank should describe a strong, intense, or sharp flavor.
- A. banal: Lacking in originality or freshness; boring. This describes a lack of interest, not flavor intensity.
- B. piquant: Having a pleasantly sharp taste or appetizing flavor; pleasantly stimulating or exciting to the mind. While "piquant" suggests a sharp or stimulating taste, it often implies a pleasant sharpness. However, in the context of pepper heat, "sharp" or "stimulating" could fit.
- C. acrid: Having an irritatingly strong and unpleasant taste or smell. This describes an unpleasant and strong taste.
- D. unique: Being the only one of its kind; unusually special. This describes distinctiveness, not flavor intensity.
- E. diverse: Showing a great deal of variety; very different. This describes variety, not flavor intensity.

Now, we need to choose between "piquant" and "acrid." Both suggest a strong taste. The sentence states "smaller peppers tend to be far more $\qquad$ than larger peppers."
Peppers are known for their varying levels of heat or spiciness. While "acrid" means strong and unpleasant, the context of "potency of flavor" in peppers often refers to their spiciness, which is not necessarily unpleasant to those who enjoy it.
"Piquant" (pleasantly sharp, stimulating) is often used for flavors that are stimulating or spicy in an enjoyable way. Many small peppers (like bird's eye chilies or habaneros) are indeed very hot or spicy, which can be described as piquant. The "potency of flavor" refers to this strong, sharp, stimulating quality.

If the opposite of "size commensurate with potency" means smaller peppers have more potency, then "piquant" would describe that strong, sharp, stimulating flavor. "Acrid" typically implies a harsh or caustic quality, which might be true for extremely hot peppers, but "piquant" captures the "sharp taste" aspect that often refers to spiciness in a broader sense. Given the options, "piquant" is a strong choice as it directly relates to a sharp, stimulating taste, which is characteristic of many small, potent peppers.

Let's re-examine the core contrast: "size is commensurate with potency of flavor" (big = strong flavor). The contrast means smaller peppers are more potent. So the blank needs a word that means "more potent/strong in flavor."
- Piquant: sharp, stimulating to the taste. This fits.
- Acrid: strong and unpleasant. While some find very spicy food unpleasant, the term "potency of flavor" in peppers primarily refers to their heat, not necessarily an unpleasantness in all contexts. Many people seek out this "potency."

Consider the common understanding: smaller peppers like jalapeños, serranos, habaneros, or ghost peppers are famous for being very hot or spicy. "Piquant" aligns with this notion of a sharp, stimulating taste.