The procedure for producing extinction in classical conditioning is to present

A) the conditioned stimulus, then the unconditioned stimulus.
B) nothing.
C) the unconditioned stimulus, followed by nothing.
D) the conditioned stimulus, followed by nothing.

In classical conditioning, extinction is the process of weakening the association between the conditioned stimulus and the conditioned response by presenting the conditioned stimulus without the unconditioned stimulus. Therefore, the best choice is D, which involves presenting the conditioned stimulus (CS) alone, without the unconditioned stimulus (US), in order to weaken the conditioned response. Choices A and C involve presenting the CS and US together, which would strengthen the association rather than weakening it. Choice B involves doing nothing, which would not actively contribute to extinction.