This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Medicine
[{'content': 'In coarctation of aoa, the side of rib notching is \nSelect and explain. \nA. Superior to rib, B. Inferior to rib, C. At sternum, D. At veebra', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Rib notching is unusual in infancy but becomes more frequent with increased age; it is present in 75% of adults with coarctation. Rib notching occurs along the inferior margin of the third to the eighth ribs; it is caused by pulsation of dilated intercostal aeries. Ref Davidson 23rd edition pg 443', 'role': 'assistant'}]