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': 'Normal body mass index is between \nSelect and explain. \nA. 16.5 - 20.5, B. 18.5 - 24.9, C. 25.0 - 29.9, D. 30.0 - 39.9', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]