Which of the following is an application of shaping?

a. A mother who wants her daughter to hit a baseball first praises her for holding a bat, then for swinging it, and then for hitting the ball.

b. A pigeon pecks a disk 25 times for an opportunity to receive a food reinforcement.

c. A rat presses a bar when a green light is on but not when a red light is on.

d. A rat gradually stops pressing a bar when it no longer receives a food reinforcement.

e. A gambler continues to play a slot machine, even though he has won nothing on his last 20 plays, and he has lost a significant amount of money.