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': 'Persistent urachus is a risk factor for: \nSelect and explain. \nA. Transitional cell ca of bladder, B. Adenocarcinoma of bladder, C. Squamous cell ca of bladder, D. Undifferentiated ca of bladder', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans is 'b' i.e. Adenocarcinoma of bladder", 'role': 'assistant'}]