Sniffy the Rat Has Been Taught to Press a Bar

Sniffy the rat has been taught to press a bar in a cage to receive food. The behavior disappeared, though, when Sniffy stopped getting food following bar-pressing. Several days later, Sniffy was put in the cage again, and he immediately began to press the bar. The reappearance of this response is called

A) reconditioning.
B) acquisition.
C) instantaneous learning.
D) spontaneous recovery.