You are presented with the question "What causes water to become steam?" and the following answer choices: 
- Condensation
 - movement of tectonic plates
 - Increasing pressure
 - an engine
 - evaporation
 - heating liquids
 - Reducing temperature
 - Adding heat energy

Now knowing that boiling means change from a liquid into a gas by adding heat energy and boiling water produces steam, choose the best answer.


 

        Adding heat energy 