The correct answer is D. Why will I be writing?
Explanation:
In writing, a prompt is a statement or short text that provides instructions about the text that should be written or suggests the main topic or idea. In this context, the first step is to clearly understand the purpose of writing, this can include to describe, explain, analyze, etc. as this purpose defines not only the main claim but the details to support this claim and the general style of the text. Moreover, the purpose can be found by asking questions such as why will I be writing? or is my purpose to entertain, describe...?
