Every Time Little Jeffrey Goes Shopping with His Mom, There

Every time little Jeffrey goes shopping with his mom, there is an incident at the checkout line when he spots candy. Typically, Jeffrey's mom initially refuses his request for a candy bar. When the child throws himself to the floor kicking and screaming, Jeffrey's mom gives in and hands him the candy bar to end the embarrassing scene. In operant conditioning terms, what is maintaining the child's "checkout tantrums"?

A) Negative reinforcement
B) Non-contingent reinforcement
C) Positive reinforcement
D) Vicarious reinforcement