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': 'One unit of packed RBC increases the blood hemoglobin by \nSelect and explain. \nA. 1 g/dl, B. 6-7 g/dl, C. 8-9 g/dl, D. None', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]