Mike and Jeff Are Brothers Who Have Just Moved with Their

Mike and Jeff are brothers who have just moved with their parents into a beautiful old house.Mike soon discovers that if he flushes the toilet while Jeff is taking a shower, it will cause the water in the shower to become scalding hot.Naturally, Jeff screams as his reflexes cause him to leap backward in pain.After Mike has repeated this procedure several times, Jeff has begun to twitch involuntarily every time he hears any toilet flush.In this example, jumping backward to the pain of the hot water would be the

A) conditioned response (CR) .
B) conditioned stimulus (CS) .
C) unconditioned response (UR) .
D) unconditioned stimulus (US) .