I say expression so D. because the more expression you put in your work the more effort will be shown. From recent studies, they have shown the more effort and expression is ideal in art.
I think the answer is audience
Gloat in the sentence means to brag. Basically, the third selection. "To make fun of someone."
Hopefully this helps :)
One good one might be that, a man would take great risks for revenge. The story is about revenge, so the easiest and best thing would be to wright about the revenge that Montresor try’s to get on his enemy. Be sure to explain why and how and what lead to his death. Hope it helps! ❤️