The answer is C.
Carbon fixation is a process that takes place during the light independent reactions of photosynthesis also referred to as the Calvin cycle.
With the help of an enzyme called RuBisCo, carbon dioxide that was captured during the light dependent reactions of photosynthesis is added to a sugar called ribulose to form a 6-carbon intermediate which breaks down immediately because it is not stable.
It breaks down to form two identical 3-carbon molecules known as 3-PGA ( 3 - phosphoglycerate)
