Han takes a shower in his family’s new apartment. He gets the water perfect—not too hot, because that hurts! Then Han hears his son flush the toilet. The water gets very hot, which makes Han feel a lot of pain. After this happens a few times, Han feels afraid when he hears a toilet flush while he is in the shower. When Han is subject to classical conditioning, the unconditioned stimulus (US) is ; the unconditioned stimulus (CS) is ; the unconditioned response (UR) is ; and the conditioned response (CR) is .

Unconditioned stimuli, US: getting hurt by hot water.Conditioned stimulus, CS: hearing a toilet flush.Unconditioned response, UR: feeling pain after hurting.Conditioned response, CR: being afraid when hearing a toilet flush.

Explanation:

Unconditioned stimuli: Biologically significant stimuli that provoke an unlearned or reflex reaction. For example, getting hurt by hot water.Conditioned stimuli: neutral, innocuous or biologically not significant stimuli. For example, hearing a toilet flush.Unconditioned Responses: Unlearned response that is triggered by reflex because of an unconditioned stimulus. For example, feeling a lot of pain after hurting by hot water. Conditioned Responses: These are provoked by conditioned stimuli. This refers to a learned response that reflects the association between conditioned and unconditioned stimuli. For example, being afraid when hearing a toilet flush.

Initially, an unconditioned stimulus does not provoke any response, but after enough exposition to conditioned and unconditioned stimuli together, the simple presence of unconditioned stimuli induces conditioned responses. In this aspect, the subject has learned to predict or to anticipate the unconditioned stimulus.

Hope the answer is b