Thirst is used to make an animal realize that it needs to replenish its bodily water by the body, and an example is H2O which shows water is made of two atoms of hydrogen stuck to one atom of oxygen. Given these facts, thirst shows an animal that it needs what among the following options:
- CO2
 - H2O
 - He
 - food
 - feed
 - urea
 - O2
 - H20


 

  H2O       