Roslyn Always Used to Shop at Penney's Because for Every

Roslyn always used to shop at Penney's because for every purchase over $20, she would get a 10 percent discount. But since Penney's stopped offering this promotion, Roslyn has stopped shopping there. Her shopping behavior (and decrease in such activities) is best explained by

A) operant conditioning.
B) classical conditioning.
C) the principle of generalization.
D) systematic desensitization.