Final answer:
In the context of game theory, the GRIM strategy enforces non-forgiveness, meaning if an opponent defects once, the player will defect indefinitely with no chance of forgiveness.
Step-by-step explanation:
A player playing a GRIM strategy will indeed never forgive his opponent's defection, so the answer is A. True. The GRIM strategy is based on the concept of non-forgiveness, which is a term used in game theory, particularly in the study of repeated games like the Prisoner's Dilemma. According to this strategy, a player cooperates with their opponent until the opponent defects (or cheats). Once the opponent defects, the player using the GRIM strategy will defect for the rest of the game, with no chance for forgiveness or a return to cooperation, no matter what the opponent does thereafter.