In Pavlov's Early Classical Conditioning Experiments, Food Was the __________

In Pavlov's early classical conditioning experiments, food was the __________, and a bell, which was originally a neutral stimulus, became a(n) __________ when paired with the food.

A) unconditioned stimulus; conditioned response
B) conditioned stimulus; unconditioned stimulus
C) unconditioned stimulus; unconditioned response
D) conditioned stimulus; unconditioned response
E) unconditioned stimulus; conditioned stimulus