The correct option is D 1
During the Calvin cycle, there is fixation of carbon dioxide and synthesis of glucose. There are three stages in the calvin cycle - carboxylation, reduction and regeneration.
During carboxylation, CO2 combines with RuBP and forms 3-PGA. RuBP is the primary acceptor of carbon dioxide. PGA undergoes reduction to form triose phosphate. Triose phosphate is recycled to regenerate RuBP. For the Calvin cycle to run continuously, it is important to regenerate the carbon accepting molecule RuBP. The regeneration step requires one ATP for phosphorylation to create one RuBP per cycle or per carbon dioxide fixed.