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': 'Squamous cell ca of urinary bladder is predisposed to by -a) Urolithiasisb) Persistent Urachusc) Schistosomiasisd) Polype) Smoking \nSelect and explain. \nA. ac, B. bc, C. ad, D. b', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Persistent urachus is a risk factor for adenocarcinoma of bladder.', 'role': 'assistant'}]