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': 'Rib notching is seen in all except \nSelect and explain. \nA. Coarctation of aoa, B. Classical blulock tausing operation, C. IVC obstruction, D. Neurofibromatosis', 'role': 'user'}, {'content': 'Answer: C \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 Non-vascular causes of rib notching include neurofibromatosis, intercostal neuromas and pseudo-rib notching where irregular coical thickening may occur in the presence of tuberous sclerosis and hyperparathyroidism. Degrees of rib notching on chest radiography may also be of no clinical significance. Ref Harrison20th edition pg 1765', 'role': 'assistant'}]