Answer:
C) conditioned to drool only when food is paired with a bell
Step-by-step explanation:
Stimulus discrimination occurs when a certain stimulus is no longer associated with its original response. This could only happen when we associate that stimuli with a specific type of situation after we encounter it over and over again.
For example, the sound of a bell usually give no effect to a dog. But if we give the dog some food every time we ring a bell, that dog will eventually associate the sound of the bell with food. In the long run, the dog will drool every time it hears a bell.