Fact 1: Acactus stem is used for storing water.

Fact 2: Water consists of H2O, etc.

Given the two facts above, answer the question "A cactus stem stores what?" with the following options: 
- RNA
 - h2o
 - rain
 - h1n1
 - co2
 - H20
 - O2
 - copper


 

  h2o       