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': 'Involucrum is \nSelect and explain. \nA. Dead bone, B. New live bone surrounding dead bone, C. Previous live bone, D. Sclerotic bone', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]