Fact 1: Thirst is used to make an animal realize that it needs to replenish its bodily water by the body.

Fact 2: Water hydrates the cells.

Given the two facts above, answer the question "Thirst is used to make animals realize they need to what?" with the following options: 
- remove their cells
 - filter their beverages
 - recovery time from fatigue
 - reusing things
 - moisturize their eyes
 - hydrate their cells
 - Converting waste.
 - they body they live in


 

      hydrate their cells   