A. Unconditioned stimulus, conditioned response, conditioned stimulus, unconditioned response
B. Conditioned stimulus, conditioned response, unconditioned stimulus, unconditioned response
C. Unconditioned stimulus, conditioned stimulus, unconditioned response, conditioned response
D. Unconditioned stimulus, unconditioned response, conditioned stimulus, conditioned response
E. Conditioned response, conditioned stimulus, unconditioned response, unconditioned stimulus