This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
Piles occurs at- 
Select and explain. 
A. Superior rectal vein, B. Inferior rectal vein, C. Superior Hemorrhoidal aery, D. None
A: Superior rectal vein
Answer: A: Superior rectal vein 
Explanation: Answer- A. Superior rectal veinInternal hemorrhoids in association with superior rectal vessels are located at 3, 7 and 11 O'clock positions corresponding to left, right posterior and right anterior branches of these vessels.