You are presented with the question "What is essential for cellular respiration?" and the following answer choices: 
- Veins and arteries.
 - kinetic energy
 - The atmosphere
 - Energy.
 - heat energy
 - Organic compounds
 - Chemical energy
 - flow of electrons

Now knowing that oxygen is essential for cellular respiration for all aerobic organisms and besides nitrogen and oxygen, the atmosphere contains many, many other molecules in trace amounts, choose the best answer.


 

   The atmosphere      