After a Painful Experience,Frederick Cringes Every Time He Hears a Dentist's

Multiple Choice

After a painful experience,Frederick cringes every time he hears a dentist's drill,even when he is sitting in the waiting room of his dentist's office.What is the pain of dental drilling in this example

A)  unconditioned response 
B)  conditioned response 
C)  conditioned stimulus 
D)  unconditioned stimulus