Carbon is released into the atmosphere
a. respiration and burning fossil fuels
b. burning of fossil fuels and photosynthesis
c. respiration and fixation
d. respiration and photosynthesis

"Carbon" releases into the atmosphere by respiration and burning of fossil fuels.  

Option A

Explanation :

Carbon releases in the form of carbon dioxide during respiration which is a result of the complete oxidation of the stored food sugar into water and carbon dioxide. Whereas, the carbon is released into the environment from the fossil fuel because these fossil fuels are made up of biomolecules such as carbon, hydrogen, nitrogen, oxygen, sulphur etc.,  and as the fossil fuel burns the bonds between these molecules break and the the elements are released into the environment.

a. decomposes use carbon from dead organisms as fuel for cellular respiration, returning carbon dioxide back into the atmosphere.

the correct answer is c   with the systems