Collusive Agreements Between Two Firms Are Most Likely to Be

Collusive agreements between two firms are most likely to be honored when the game

A) is a one-time game with the opportunity for a prisoner's dilemma.
B) has a Nash equilibrium that differs from the outcome that maximizes the payoffs to the two firms.
C) is a zero-sum game.
D) is repeated and both firms offer credible threats if the other violates the agreement.