Answer:
Humans release carbon dioxide (CO2) into the atmosphere through cellular respiration. This CO2 is used by plants during photosynthesis. During photosynthesis, plants release oxygen (O2) into the atmosphere. The oxygen is used by animals in order to carry out cellular respiration.
Explanation:
I put all I know into that so it should be right but if it isn't then I'm sorry
The cell wall because of the fact it is present in the plant cell and not in the animal cell
The seven units that form the basis for all derived units in the metric system are called the base units. Math: Powers of ten. Language: Prefixes. Kilograms: another kind of measurement. Hope this helped :)