This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: NEET Jan 2020, Subject name: Radiology
Chest radiograph obtained from a male patient with hypeension, What could be the probable diagnosis? 
Select and explain. 
A. Mitral Stenosis, B. Coarctation of Aoa, C. Transposition of Great Aeries, D. Aoic Stenosis
B: Coarctation of Aoa
Answer: B: Coarctation of Aoa 
Explanation: The CXR shows "3-sign" which is characterstic of Coarctation of aoa Coarctation of Aoa Inferior rib noching is seen and is due to pressure erosion by intercoastal aeries Rib notching is usually bilateral but assymetrical and mostly spares first two ribs The 3-sign appearance in CXR is due to enlargement of left subclan aery above the coarctation. Reverse 3 sign is seen in barium swallow in coarctation of aoa.