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: Radiology
[{'content': 'The most impoant investigation for posterior urethral value is: \nSelect and explain. \nA. Urethroscopy, B. IVP, C. Retrograde cystogram, D. Micturating cystogram', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. Micturating cystogram', 'role': 'assistant'}]