Which of the Following Is Not True

Which of the following is not true?

A) Collusion is relatively rare, in part because it is illegal in many countries.
B) Collusion is relatively rare, even though members find it easy to agree on key decisions.
C) Collusion is relatively rare, in part because members frequently have an incentive to cheat on the cartel.
D) Collusion is harder to maintain when differentiated products are involved, which introduce many ways to undercut a collusive agreement.