Collusion Makes Firms Better Off Because If They Act as a Single

Collusion makes firms better off because if they act as a single entity (a cartel) they can reduce output and increase their prices and profits.But some cartels have failed and others are unstable.Which of the following is a reason why cartels often break down?

A) Most cartels do not have a dominant strategy.
B) When a cartel is profitable, the amount of competition it faces increases.
C) Members of a cartel may resent having to share their profits equally.
D) Each member of a cartel has an incentive to "cheat" on the collusive agreement by producing more than its share when everyone else sticks with the collusive agreement.