You are presented with the question "what is used to make an animal realize that it needs to replenish from a natural drinkable source" and the following answer choices: 
- spring
 - excretion
 - blood
 - pain
 - thirst
 - tiredness
 - hunger
 - rain

Now knowing that thirst is used to make an animal realize that it needs to replenish its bodily water by the body and water Water in the area's natural water bodies is drinkable as such, choose the best answer.


 

     thirst    