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 common cause of renovascular hypertension in children and young adults \nSelect and explain. \nA. Atherosclerotic disease, B. Fibromuscular dysplasia, C. Ectopic kidney, D. PCKD', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]