Topic: Interchange of Parts of Speech,

Best Answer Explained in Below-:

The word "brevity" is a noun that refers to the quality of being brief or concise in expression. To transform this noun into its adjective form, we look for a word that describes the state of being brief. In this case, the correct adjective is "brief" (option C).

Here’s why the other options do not fit:

- **A) Brave**: This is an adjective that describes someone who is courageous or shows bravery, and it is unrelated to the concept of brevity.

- **B) Bravery**: This is a noun that embodies the quality of being brave, again unrelated to brevity.

- **D) Briefly**: This is an adverb, which modifies verbs, adjectives, or other adverbs and indicates the manner in which something is done, but it does not serve as an adjective.

In summary, "brief" is the appropriate adjective derived from the noun "brevity," as it directly describes the characteristic of being short in duration or concise in expression, thus making option C the correct answer.