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': 'Which of the following causes rib-notching on the chest radiograph? \nSelect and explain. \nA. IVC occlusion, B. Coarctation of aoa, C. Bidirectional Glem shunt, D. Modified Blalock-Taussing shunt', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Coarctation of aoa is associated with notching, typically of the inferior posterior aspects of the ribs (3rd through 8th). The number and location of notched ribs provides information regarding location of the coarctation. Ref: CURRENT Diagnosis & Treatment: Nephrology & Hypeension chapter 42; Essence of Paediatrics By Khan, 4/e page 153-8.', 'role': 'assistant'}]