This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
In ETC, Oxidative phosphylaion (ATP formation) is regulated by: 
Select and explain. 
A. NADH Co-Q reductase, B. Cytochrome C oxidase, C. Co-Q-Cytochrome C reductasev, D. All of the abobe
D: All of the abobe
Answer: D: All of the abobe 
Explanation: A, B, C i.e. (NADH Co-Q reductase, Cytochrome C oxidase, Co-Q-Cytochrome C reductase) Mitchell's chemiosmotic hypothesis links the respiratory (i.e. electron transpo) chain to ATP production (i.e. oxidative phosphorylation)Q. It explains how the free energy generated by the transpo of electrons from NADH to molecular oxygen (in respiratory chain) is used to produce ATP from ADP + Fi (from proton pumps). For each NADH oxidized (pair of electron), complex I (NADH -Q- oxido reductase) and complex III (ubiquinone /Qcytochrome C- oxidoreductase) pump (translocate) 4 protons (H+) each, whereas complex IV (Cytochrome C- oxidase) translocates only 2 protons (H+). In ETC. oxidative phosphorylation (ATP formation) occurs at these sites (ie complex I, III & IV)