In classical conditioning, the is an unlearned reaction to a given stimulus. for example, if you have an allergy to pollen and sneeze, sneezing is an unlearned reaction to the pollen (i. e., the stimulus).a. conditioned response
b. conditioned stimulus
c. unconditioned response
d. unconditioned stimulus

c. unconditioned response

Explanation:

In psychology and classical conditioning, an unconditioned response is a reaction that is not learned and that happens naturally as a reaction to some other stimulus (which is called the unconditioned stimulus). This stimulus is the one that will later be paired to another one and then the originally unconditioned response will appear (as a learned behavior) in presence of the second stimulus (and it will be called conditioned response).  

Therefore, we can say that the unconditioned response is an unlearned reaction to a given stimulus.

i got 3,4 and 5 as an answer