Fact 1: Clouds are formed by water vapor rising into colder regions of the atmosphere and condensing.

Fact 2: Water is made up of H2O molecules.

Given the two facts above, answer the question "what vapor forms clouds by rising into the atmosphere condensing?" with the following options: 
- rain
 - lightning
 - greenhouse gas
 - H20
 - SO2
 - pollution
 - h2o
 - Dew


 

       h2o  