Which Situation Is an Example of Grudge Stalking

Which situation is an example of grudge stalking?

A) Mike is infatuated with a classmate and checks her social media accounts constantly.
B) Carlos falsely believes that the professor he has never spoken to is secretly in love with him.
C) Leon calls the woman he asked out a rude name when she turns him down.
D) John shows up wherever his ex-boyfriend happens to be.
E) Doug follows around the supervisor who fired him because he likes making that person feel scared.