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
Commonest cause of A-V fistulae is - 
Select and explain. 
A. Congenital, B. Traumatic, C. Surgical creation, D. Tumour erosion
A: Congenital
Answer: A: Congenital 
Explanation: Ans. is 'a' i.e., Congenital