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': '"Marble bone" appearance is characteristic of: \nSelect and explain. \nA. Osteopetrosis, B. Osteogenesis imperfecta, C. Fluorosis, D. Achondroplasia', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. Osteopetrosis', 'role': 'assistant'}]