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': '"Marble Bone" appearance is seen in: March 2009 \nSelect and explain. \nA. Osteomalacia, B. Osteopetrosis, C. Rickets, D. Osteoporosis', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B: Osteopetrosis Osteopetrosis/marble bone disease/Albers-Schonberg disease is a disorder characterized by dense but brittle bones (marble bones)', 'role': 'assistant'}]