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': "Marion's disease is due to - \nSelect and explain. \nA. Muscular hypertrophy of internal sphincter of urinary bladder, B. Fibrosis of the neck of bladder, C. Vesicular diverticula, D. Vesicular calculi", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]