C. is the correct answer and BTW I don't know if it was U or not there was a question about when the carbon is realised from non living to living environment the answer to that question would be photosynthesis
There is some carbon released during cellular respiration as carbon dioxide C6H12O6 + 6O2 = 6CO2 + 6H2O + 36 or 38 ATP but there is so much more released when the plant dies and rots that I think the answer they want is C.
