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': 'Notching of the ribs is seen in man \nSelect and explain. \nA. TR, B. TOF, C. Coarctation of aoa, D. PDA', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Coarctation of aoa', 'role': 'assistant'}]