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: Answer is D (Biopsy): Although ultrasonography and CT scan can be useful in making a diagnosis of medullary cystic disease, an open renal biopsy that ensures recovery of tissue from the coicomedullary junction is definitive.', 'role': 'assistant'}]