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': 'Sq. cell tumor of urinary bladder is due to ? \nSelect and explain. \nA. Stone, B. Schistosomiasis, C. Chr. cystitis, D. All', 'role': 'user'}, {'content': "Answer: D \nExplanation: Answer is 'a' i.e. Stone 'b' i.e. Schistosomiasis & 'c' i.e. Chronic cystitis", 'role': 'assistant'}]