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
[{'content': 'Cytochrome oxidase contains: \nSelect and explain. \nA. Mg, B. Cu, C. Both of the above, D. None of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Cu', 'role': 'assistant'}]