When the Family Dog Licks the Faces of the Children

Multiple Choice

When the family dog licks the faces of the children in the family,they laugh and give the dog a treat.When the dog licks the faces of the parents,they scold the dog.As a result,the dog no longer licks the faces of the parents,but continues to lick the faces of the children.The parents' faces would be an example of a(n) _________ for the dog licking their faces:​

A) ​negative reinforcer
B) ​S-delta
C) ​unconditioned stimulus
D) ​discriminative stimulus