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: Radiology
[{'content': '"Bone within a Bone" appearance is \nSelect and explain. \nA. Osteogenesis imperfecta, B. Osteopetrosis, C. Scurvy, D. Rickets', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Osteopetrosis', 'role': 'assistant'}]