You are presented with the question "What causes water to expand as it becomes ice?" and the following answer choices: 
- evaporation
 - wind
 - Weathering
 - heat
 - gasoline
 - Generating heat
 - friction
 - hydrogen bonds

Now knowing that hydrogen bonds cause water to expand when it freezes and water freezes into ice when cooled, choose the best answer.


 

        hydrogen bonds 