Answer:
absorption of oxygen
Explanation:
the others would not make sense so i think this is the answer
The answer is A. Uses too much energy.
4 significant figures I think
Because they are the same chemical reaction but reversed. Cellular respiration takes glucose (from nutrient/food) and oxygen (from atmosphere) in order to make CO2 (think about exhaling) and H20 (water).
(I don't remember this clearly so it may be wrong, i'll look into it and come back!)