the correct combo is C
We know sunlight is key factor in photosynthesis so A and D are out.
we also know plants get their bulk by breaking up co2 and using the carbon which releases oxygen as a byproduct so B is also out of the question.
Answer : The total number of atoms in the product are, 36 atoms.
Explanation :
Balanced chemical reaction : It is defined as the reaction in which the number of atoms of individual elements present on reactant side must be equal to the product side.
When 1 molecule of glucose reacts completely with 3 molecules of oxygen then it react to give 6 molecules of carbon dioxide and 6 molecules of water.
The balanced chemical reaction will be:

There are 3 atoms in carbon dioxide and 3 atoms in water.
Total number of atoms in the product = 6(3) + 6(3) = 36 atoms
Thus, the total number of atoms in the product are, 36 atoms.
D) because both reactions are occurring at the same rate. They are not equal but their concentrations are constant.
hydrogen and carbon, hope that helped