After he was spanked on several occasions for spilling his milk at a restaurant, colin became afraid to go to the restaurant. in this case, spanking was a(n) for colin's fear.
a. negative reinforcer
b. conditioned stimulus
c. secondary reinforcer
d. unconditioned stimulus

Unconditional stimulus

Explanation:

Classical conditioning is a major area of psychology that contributes to the school of psychology is behaviorism. Classical conditioning was proposed by Russian psychologist Ivan Pavlov. Classical conditioning was learning behavior through the association between stimulus and subjects.

In this conditioning, the behavior depends on the assumptions. Environmental condition shapes the behavior of human being as well as animals. Unconditioned stimulus was the part of classical conditioning. It occurs naturally, automatically that triggers the response of a person.  

For example here in the above statement spanking is an unconditioned stimulus because he was spanked on many occasions because of spilling milk. Now he afraid to restaurant

answer; i believe the correct answer is (8) eight.

your answer is "graduates" hope this