This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Aerial disorders, Subject name: Surgery
Commonest pa of subclan aery to be affected by Stenosis is: 
Select and explain. 
A. First pa, B. Second pa, C. Third pa, D. Equally affected
A: First pa
Answer: A: First pa 
Explanation: MC site of subclan aery Stenosis is the first pa of the subclan aery.