Alex Loves to See His Girlfriend Smile

Multiple Choice

Alex loves to see his girlfriend smile. When he stops on the way home from the office to pick up a little gift for her, she gets the biggest smile on her face when he gives it to her. According to the principles of operant conditioning, Alex stops to buy her gifts more and more frequently because

A) her smile reinforces his behaviour
B) if she doesn't smile he feels deflated
C) it takes increasingly more gifts to make her smile
D) he rewards her smiling with the gifts