In the initial step in carbon fixation, a molecule of CO₂ is attached to RuBP to produce a sixcarbon molecule, which is immediately split to produce two molecules of 3 -phosphoglycerate. After phosphorylation and reduction produces glyceraldehyde 3-phosphate (G3P), what more needs to occur to complete the Calvin cycle? a. Addition of a pair of electrons from NADPH b. Regeneration of ATP from ADP c. Regeneration of RuBP d. Regeneration of NADP⁺