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
Which component transfers four protons: 
Select and explain. 
A. NADH-Q Oxidoreductase, B. Cytochrome -C oxidase, C. Cytochrome C - Q oxidoredictase, D. Isocitrate Dehydrogenase
A: NADH-Q Oxidoreductase
Answer: A: NADH-Q Oxidoreductase 
Explanation: A i.e. NADH-Q Oxidoreductase; C i.e. Cytochrome C-Q oxidoreductase