3 (I think, sorry if it’s wrong)
Well, I'm assuming you're talking about these terms...
Species, Genus, Family, Order, Class, Phylum, Kingdom, Domain
A good way to remember this is;
Does King Philip Come Over For Great Spaghetti
(However, this is in order from most specific to least specific)
Cells get energy for their functioning through sunlight and other organic food molecules. ATP is a good example of energy pathways through photosynthesis.
Answer:
The plant is photosynthesizing and using up the CO2.