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': 'In coarctation of aoa the rib changes are seen from: \nSelect and explain. \nA. 1-12th, B. 3-6th, C. 4-9th, D. 8-12th', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. 4-9th', 'role': 'assistant'}]