Fact 1: Boiling means change from a liquid into a gas by adding heat energy.

Fact 2: Gas is the source of energy for heating water and for the stove.

Given the two facts above, answer the question "What heats water for boiling?" with the following options: 
- water
 - ice
 - magnets
 - Heat
 - ligt
 - fire
 - gas
 - salt


 

       gas  