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: Surgery
[{'content': 'The spleen contains about _________% of the total blood volume \nSelect and explain. \nA. 1, B. 2, C. 5, D. 7', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]