Which prompt would be best addressed with a compare-and-contrast structure?

The answer is a you are comparing the two

As with all interpretive questions, your answer is based upon your own reading of the story and how you analyze the plot and characters. Rainsford had escaped Zaroff, and won the game. There was no reason to return to the masion and kill Zaroff except to exact revenge. Consider that Rainsford himself is a hunter, used to being in power. Although he had never considered doing something as inhumane as Zaroff in hunting humans, his choice to kill Zaroff reveals his need to be in control. In this case, his killing of Zaroff isn't about justice, but about revenge.