Boiling is when liquids are heated above their boiling point, and boiling is the conversion of a liquid to a gas. Given these facts, what converts liquid to gas among the following options:
- Stirring it
 - Fuel cells
 - circulatory systems
 - Cooling it down
 - Introducing oxygen
 - Heating it up
 - Evaporation
 - water vapor


 

      Heating it up   