You are presented with the question "What is something people can survive only a few days without?" and the following answer choices: 
- Shelter
 - Food
 - O3
 - NaCl
 - urea
 - H20
 - H2O
 - Salt

Now knowing that most people can survive only a few days without water and water is made up of H2O molecules, choose the best answer.


 

       H2O  