You are presented with the question "what cannot surive without oxygen" and the following answer choices: 
- basic building blocks of life
 - Microscopic organisms
 - an area swollen with pus
 - incapable of regurgitation
 - hydrogen
 - vacuum
 - outer space
 - the respiratory system

Now knowing that cells cannot survive without oxygen and cells are the basic building blocks of life, choose the best answer.


 

 basic building blocks of life        