You are presented with the question "what vapor forms clouds by rising into the atmosphere condensing?" and the following answer choices: 
- rain
 - lightning
 - greenhouse gas
 - H20
 - SO2
 - pollution
 - h2o
 - Dew

Now knowing that clouds are formed by water vapor rising into colder regions of the atmosphere and condensing and water is made up of H2O molecules, choose the best answer.


 

       h2o  