This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Contraception, Subject name: Gynaecology & Obstetrics
[{'content': 'Failure rate of vasectomy is : \nSelect and explain. \nA. 0.20%, B. 0.50%, C. 3%, D. 10%', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Failure rate us about 0.5% TEXTBOOK OF GYNECOLOGY SHEILA BALAKRISHNAN SECOND EDITION PAGE NO 396', 'role': 'assistant'}]