two sticks being rubbed together a piece of wood burning steel wool rusting ice cubes melting
I gave my students this multiple choice question: Which of the following will absorb heat energy?

Only one answer is correct among these 4 choices:
- two sticks being rubbed together
- a piece of wood burning
- steel wool rusting
- ice cubes melting

Could you tell me which one is correct?

ice cubes melting