Answer: The answer is D.
Step-by-step explanation:
Option A is not the answer because sometimes headings would not make as much sense or include a sufficient amount of information in order to understand the message an author is trying to send. Option B is not the answer because (most of the time) an author's background is irrelevant to determining the message they're trying to send through their works. Option C is not the answer because the amount of information itself does not determine an author's message. Option D is the answer because the usage of specific words helps determine the tone and feeling (and ultimately, the message) the author is trying to send across to the reader.