Ivan Conditioned His Pet Bloodhound, Watson, to Drool Every Time

Ivan conditioned his pet bloodhound, Watson, to drool every time the doorbell rang. After a few weeks, he got tired of mopping up the puddle of drool by his front door, so he repeatedly rang the doorbell without pairing the sound with food. Eventually, the process of _____ occurred, and Watson stopped drooling every time the doorbell rang.

A) learned helplessness
B) stimulus discrimination
C) instinctive drift
D) extinction