The answer is C. The Calvin cycle occurs in the stroma o the chloroplast in a plant cell. It involves the dark stage where carbon dioxide is reduced by protons created in photolysis from the light stage of photosynthesis. The 3-phosphoglyceric acid (3-PGA) is phosphorylated by ATP and then immediately reduced by NADPH in the reduction step. After reduction, G3P is formed and exits the cycle. Other G3Ps are regenerated into a ribulose-1,5-bisphosphate (RuBP) acceptor molecule for the cycle to continue.
