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
In coarctation of aoa, the side of rib notching is 
Select and explain. 
A. Superior to rib, B. Inferior to rib, C. At sternum, D. At veebra
B: Inferior to rib
Answer: B: Inferior to rib 
Explanation: 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