Fact 1: Acactus stem is used for storing water.

Fact 2: When the rain stops the cactus is fat because the cactus roots drink the water.

Given the two facts above, answer the question "When the rain stops the stem used for storing water is fat because the what drink the water" with the following options: 
- animals
 - liquid
 - lipids
 - skin
 - fatty
 - fibrous
 - leaves
 - roots


 

        roots 