Extinction occurs when ____________.
a. the conditioned stimulus is presented repeatedly without being paired with an unconditioned stimulus
b. the unconditioned stimulus is presented repeatedly without being paired with a conditioned stimulus
c. the neutral stimulus is presented repeatedly without being paired with an unconditioned stimulus
d. the neutral stimulus is presented repeatedly without being paired with a conditioned stimulus.
Answer: a. the conditioned stimulus is presented repeatedly without being paired with an unconditioned stimulus