Correct Answer - C
Reductive carboxylation start with a 5 carbon sugar ribulose-5 phosphate. 6 mol of this sugar react with 6 mol of ATP (produced in light reaction) to form 6 mol of RuBP and 6 mol ADP.
Ribulose -5 phosphate `overset("Phosphopentakinase")to` Ribulose 1,5-biphosphate+6ADP