Here's why:
* Comparative adjectives and adverbs are used to compare two things. In this case, we are comparing the quietness of Carol's current office to the quietness of a desired office.
* The word "quieter" is the comparative form of the adjective "quiet".
Let's break down the other options:
* Positive: The positive degree is the base form of the adjective (e.g., quiet).
* Superlative: The superlative degree is used to compare three or more things (e.g., quietest).