The Production of Glyceraldehyde 3-Phosphate G3P) in the Calvin Cycle

The production of glyceraldehyde 3-phosphate G3P) in the Calvin cycle requires six molecules each of ATP and NADPH. Another three molecules of ATP are then used in the cycle. What is the purpose of the three additional ATP molecules?

A) to regenerate the starter molecule RuBP
B) to attract the next CO₂ molecule to enter the Calvin cycle
C) to reduce the molecules of G3P to form glucose
D) to join acetyl CoA into pyruvate, preparing it to enter the citric acid cycle
E) to fix carbon dioxide to RuBP