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': 'Most important investigation for posterior urethral valve is – \nSelect and explain. \nA. Urethroscopy, B. IVP, C. Retrograde cystogram, D. Micturating cystogram (MCU)', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Micturating cystourethrogram (MCU) provides the radiological basis for the diagnosis of posterior urethral valve.', 'role': 'assistant'}]