This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Musculoskeletal Radiology, Subject name: Radiology
[{'content': 'Bone within bone appearance is feature of? \nSelect and explain. \nA. Fibrous Dysplasia, B. Osteopetrosis, C. Osteogenesis Imperfecta, D. Osteoporosis', 'role': 'user'}, {'content': 'Answer: B \nExplanation: - Bone within Bone Appearance is seen in Osteopetrosis other causes of bone within bone appearance is: Sickle cell disease osteomyelitis Caffey disease Bone healing hypervitaminosis D Pagets disease acromegaly', 'role': 'assistant'}]