Name a organism that does most of the earth’s nitrogen fixation for the nitrogen cycle

Carbon fixation only takes place in autotrophs. For example plants, algae, and some bacteria, or organisms that make their own food.

the calvin cycle has three stages. in stage 1, the enzyme rubisco incorporates carbon dioxide into an organic molecule. in stage 2, the organic molecule is reduced. in stage 3, rubp, the molecule that starts the cycle, is regenerated so that the cycle can continue

looks like the answer is     c     to me!