Which of the Following Is/are Examples of Ways to Curtail

Which of the following is/are examples of ways to curtail aggression among athletes?

A) The penalty or punishment that an athlete receives for an act of aggression must be of greater punitive value than the potential reinforcement for committing the act.
B) External stimuli or cues capable of evoking aggression should be removed.
C) Coaches and referees should be encouraged to attend in-service training workshops for dealing with aggression on the part of players.
D) All of the above.