You are presented with the question "what freezes and thaws to cause ice wedging?" and the following answer choices: 
- h2o
 - dams
 - oxygen
 - clouds
 - carbon
 - rain
 - lake
 - H20

Now knowing that cycles of freezing and thawing water cause ice wedging and water is made up of H2O molecules, choose the best answer.


 

 h2o        