You are presented with the question "What converts liquid to gas?" and the following answer choices: 
- Stirring it
 - Fuel cells
 - circulatory systems
 - Cooling it down
 - Introducing oxygen
 - Heating it up
 - Evaporation
 - water vapor

Now knowing that boiling is when liquids are heated above their boiling point and boiling is the conversion of a liquid to a gas, choose the best answer.


 

      Heating it up   