Mark and Kathy Take Their Two-Year-Old Son to the Supermarket

Mark and Kathy take their two-year-old son to the supermarket every Saturday. Each week, the same sequence of events unfolds: their son screams, demanding that they buy him treats. Although they refuse to give in to his demands, he continues to scream. Finally, either Mark or Kathy gets in their son's face and yells at the top of their lungs "Shut up!" He stops screaming instantly. What operant conditioning concepts are illustrated in this story?

A) The parents are using negative reinforcement to increase their son's screaming.
B) The parents are using punishment to suppress the screaming; their use of punishment is negatively reinforced by the cessation of screaming.
C) Their son probably learned how to scream by observing his parents at home, and now he is reinforced on a variable-interval schedule of reinforcement.
D) Their son probably learned how to scream by observing his parents at home, and now he is reinforced on a fixed-ratio schedule of reinforcement.