In a Memory Study, a Rat Is Trained in Phase

In a memory study, a rat is trained in Phase 1 to press whichever key light is flashing (sometimes the left, sometimes the right) in order to get food. In Phase 2, the same rat is taught to press the illuminated left key in order to get food (constant illumination) and ignore the right key light (constant illumination) , which now is associated with no food. Phase 3 returns to the randomized flashing light signal of Phase 1. If the rat in Phase 3 tends to press the flashing left but not the flashing right key, this faulty responding is likely due to

A) proactive interference.
B) retroactive interference.
C) encoding failure.
D) trace decay.