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: Medicine
[{'content': 'Each milliliter of red cells contains ....... mg of elemental iron: \nSelect and explain. \nA. 1 mg, B. 2 mg, C. 3 mg, D. 4 mg', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Each milliliter of red cells contains 1 mg of elemental iron. Reference: Harrisons Principles of Internal Medicine, 18th Edition, Page 845', 'role': 'assistant'}]