Hello! I would say the narrator is insane because he can still hear the old man’s heart thumping from underneath the floorboards even after he killed him. His guilt gets the better of him and he turns himself in to the cops. I don’t have any evidence sense I don’t have the story on me, but use something from the story along the lines where he “hears” the thumping of his heart as evidence.
The answer is C. Please pay attention in SAT/ACT prep you won't believe how useful it is in the future, take it from someone who just took the SATs.
