At boxing practice, Nathan works with his coach to improve the strength of his punch. Nathan says that the reason the bag is heavy is so that it can absorb plenty of elastic potential energy. Is he correct?

Answer Choices
A. Yes, he is correct.
B. No, the bag absorbs thermal energy.
C. No, the bag absorbs gravitational potential energy.
D. No, the bag is heavy so that its mass will only accelerate a small amount when he punches it.