Alan Always Turns the Aquarium Light on Before Putting Fish

Multiple Choice

Alan always turns the aquarium light on before putting fish food into the tank. After a while he notices that the fish swim to the top to look for the food as soon as he turns on the light. In this example, the
__________ is the unconditioned stimulus.

A) presence of Alan near the aquarium
B) fish swimming to the top
C) aquarium light
D) fish food