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
[{'content': 'Commonest cause of A-V fistulae is - \nSelect and explain. \nA. Congenital, B. Traumatic, C. Surgical creation, D. Tumour erosion', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Congenital", 'role': 'assistant'}]