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': 'The accurate diagnostic aid in renal artery stenosis is - \nSelect and explain. \nA. Selective renal angiography, B. Ultrasound, C. CT scan, D. IVU', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]