I think it's D because it's the main thing
The main purpose of subheadings are:
They stand out because of their size and attract attention.
The scanner will stop to read them and continue scanning until the next subhead which they'll then read.
<em>Hi There!!</em>
<em>I think the best answer is </em><em>Clause</em><em>...</em>
<em>Hope This Helps!!</em>

you should not mistreat somebody or something if they have done nothing to harm you