Fact 1: Acactus stem is used for storing water.

Fact 2: Photosynthesis occurs on the green surface of the cactus stem.

Given the two facts above, answer the question "Where photosynthesis occurs in a cactus, what is stored?" with the following options: 
- glucose
 - flowers
 - water
 - sand
 - gametes
 - birds
 - lipids
 - energy


 

   water      