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
Involucrum is 
Select and explain. 
A. Dead bone, B. New live bone surrounding dead bone, C. Previous live bone, D. Sclerotic bone
B: New live bone surrounding dead bone
Answer: B: New live bone surrounding dead bone 
Explanation: None