One of the Best Ways for Teachers Who Observe Other

One of the best ways for teachers who observe other students being insensitive to the feelings and needs of other students to react to the behavior is to

A) make it a rule that you don't treat people like that.
B) ignore the behavior and let the students work it out.
C) find a way to sensitize the students involved to the implications of their behavior and let them know it is not acceptable to you.
D) make sure that those students do not get a chance to interact with each other in your class.