An author can try to give the thoughts of the character or maybe a flashback from the past that reader doesn’t know about yet.
The part where Zaroff tried to include Rainsford in his sick hunting game would be the best portray Zaroff as Rainsford's foil i think.
Beside that, they both actually are very similar with one another
Answer: "It's a dog" and "Who's that?"
Explanation:
The comma is putting together and shortening 'it is' and 'who is'.
