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
Iron is present in all, EXCEPT 
Select and explain. 
A. Myoglobin, B. Cytochrome, C. Catalase, D. Pyruvate kinase
D: Pyruvate kinase
Answer: D: Pyruvate kinase 
Explanation: None