Answer the following question given this paragraph: 

To prepare coal for use, the coal is first crushed into powder and burned in a furnace. Like other fuels, coal releases most of its energy as heat when it burns. The heat from the burning coal is used to boil water. This makes steam. The steam spins turbines, which creates electricity.


Q: When does coal release most of its energy?

 Choices:

- when forming

- when compressed

- when falling

- when burning

A:
when burning
