Answer: C- through the membrane
Step-by-step explanation:
The molecules of NADH and FADH2 resulting from the of Krebs (by the reduction, respectively, of NAD + and FAD) carriers of electrons and protons (e- and H +), are oxidized in the final reactions of cellular respiration, and the electrons and protons are picked up by oxygen, the final acceptor. Electron transport occurs in the intermembrane space. The electron transport chain contains 3 large protein complexes in the inner membrane of mitochondria; a small protein - cytochrome c; and a non-protein component - ubiquinone (Q).