Fact 1: Astem is used to store water by some plants.

Fact 2: Water is made up of H2O molecules.

Given the two facts above, answer the question "what do some plants use a stem to store?" with the following options: 
- CO2
 - H20
 - RNA
 - UV
 - urea
 - Dew
 - h2o
 - rain


 

       h2o  