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': 'Lipoma becomes malignant commonly at which site \nSelect and explain. \nA. Subcutaneous, B. Retro-peioneal, C. Sub-aponeurotic, D. Intermuscular', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Retro- peritoneal", 'role': 'assistant'}]