Oxidative phosphorylation, the synthesis of ATP in the presence of O₂, occurs in:

Explanation

Oxidative phosphorylation, which is the process of synthesizing ATP using oxygen, takes place on the inner membrane of mitochondria. This membrane houses the electron transport chain and ATP synthase, which together produce most of the cell's ATP. The other options are incorrect because the cytoplasm carries out glycolysis (not oxidative phosphorylation), the outer mitochondrial membrane serves only as a protective barrier, and the chloroplast stroma is involved in photosynthetic reactions, not in oxygen-dependent ATP production. Thus, the correct site of oxidative phosphorylation is the mitochondrial inner membrane.