Which of the following is demonstrating extinction of an operant response?
a. Ron, who receives praise every time he puts his schoolbooks away
b. Harry, who learns secret routes that provide an escape from the Dark Forest when he is under attack
c. Ginny, who learns to dress herself when her mother reinforces her for accomplishing each small step in the process
d. Hermione, who eventually stops raising her hand when Professor Snape fails to call on her