Every Time Bert Slices Onions, the Onions Burn His Eyes

Multiple Choice

Every time Bert slices onions, the onions burn his eyes and tears run down his face. One day he opened the silverware drawer and pulled out the knife that he uses only to peel onions and immediately started to shed tears from the sight of the knife. In this situation, the onion is the __________, and the knife is the __________.

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