Although nitrogen gas makes up 78% of the atmosphere, we can't use it because

nitrogen atoms must be broken apart first before.

it is prolly d and c and f

the calvin cycle takes place in the stroma of the chloroplast. carbon dioxide enters the stroma of the chloroplast to combine with the five-carbon compound called ribulose1, 5-biphosphate to form two molecules of a three-carbon compound called 3-phosphoglyceric acid. this reaction is catalyzed by an enzyme called ribulose bi-phosphate carboxylase.