While Out Trick-Or-Treating for Halloween, at First, Billy's Neighbors Had

Multiple Choice

While out trick-or-treating for Halloween, at first, Billy's neighbors had to remind him to say "Trick or treat" before they dropped their treats into his bag. As he continued to visit houses in the neighborhood, soon Billy would say "Trick or treat" as soon as the neighbors answered the door. The treats he received were the _____ for his saying "Trick or treat."

A) conditioned stimulus
B) reinforcement
C) reward
D) discriminative stimulus