You are presented with the question "What is used by animals to realize their bodies need hydration?" and the following answer choices: 
- shelter
 - keratin
 - fever
 - excretory
 - Enzymes
 - thirst
 - food
 - sores

Now knowing that thirst is used to make an animal realize that it needs to replenish its bodily water by the body and every body needs plenty of hydration, and water is the best source of that hydration, choose the best answer.


 

      thirst   