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: Physiology
[{'content': 'The enzyme system which continuously reduces ferric form of iron in the blood to the ferrous form is \nSelect and explain. \nA. Methemoglobin reductase, B. Chymotrypsin, C. Amylase, D. Dehydrogenase', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]