Fact 1: Hydrogen bonds cause water to expand when it freezes.

Fact 2: Water is made up of H2O molecules.

Given the two facts above, answer the question "What bonds cause H2O to expand when freezing?" with the following options: 
- Covalent
 - Hydrogen
 - Metallic
 - an ion
 - Heat energy
 - Ionic
 - heat
 - an anion


 

  Hydrogen       