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: Medicine
[{'content': 'Medullary cystic disease of the kidney is best diagnosed by - \nSelect and explain. \nA. Ultrasound, B. Nuclear scan, C. Urography, D. Biopsy', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]