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': "'String of beads' or sausage appearance of the renal aery is due to: \nSelect and explain. \nA. Fibromuscular dysplasia, B. Subadventitial fibroplasia, C. Medial fibroplasia with aneurysms, D. Outercoat fibroplasia with aneurysms", 'role': 'user'}, {'content': 'Answer: A \nExplanation: Fibromuscular dysplasia', 'role': 'assistant'}]