This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Urethra & Penis, 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: Ans. (a) Muscular hypertrophy of internal sphincter of urinary bladder* Congenital hypertrophy of the posterior urethra due to muscular hypertrophy and stenosis at bladder neck is known as Marion's disease.", 'role': 'assistant'}]