Final answer:
In classical conditioning, an unwanted reaction to a given stimulus is called a conditioned response, which is a learned reaction to a stimulus that did not originally produce the response.
Step-by-step explanation:
In classical conditioning, an unwanted reaction to a given stimulus is known as a conditioned response (d). Conditioned responses are learned reactions to conditioned stimuli that did not originally produce the response. For instance, if a dog has been conditioned to feel anxiety at the edge of a yard due to an invisible electric fence (where the electric shock is an unconditioned stimulus and the anxiety is an unconditioned response), that anxiety becomes a conditioned response when it occurs in reaction to the conditioned stimulus, which is the edge of the yard after conditioning. The process of learning to associate the electric shock with the edge of the yard transforms the neutral stimulus (the edge of the yard) into a conditioned stimulus. Extinction of this conditioned response can occur if the electric shock (unconditioned stimulus) is no longer presented alongside the conditioned stimulus (the edge of the yard), leading to a gradual decrease and loss of the conditioned response.