Pavlov noticed that dogs began salivating at the mere sight of the person who regularly brought food to them. for the dogs, the sight of this person was a(n) a) spontaneous recovery. b) unconditional stimulus. c) secondary conditioner. d) conditioned stimulus.

d) conditioned stimulus                    

Explanation:

Conditioned stimulus: The term has been first used in the classical conditioning experiment and can be widely applied in the day to day life.

Therefore, the conditioned stimulus in classical conditioning is a stimulus that was neutral earlier and after being associated with an unconditioned stimulus then it gives rise to a conditioned response.

In the question above, for the dogs, the sight of this person was a conditioned stimulus.

the answer is:

c. economic output