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': 'Iron is present in all of the following except \nSelect and explain. \nA. Myoglobin, B. Cytochrome, C. Catalase, D. Pyruvate Kinase', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]