This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Non-Hormonal - Barrier Methods, Subject name: Gynaecology & Obstetrics
[{'content': 'Today vaginal sponge failure rate is? \nSelect and explain. \nA. 5%, B. 9%, C. 16%, D. 20%', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. (b) 9%Ref: Appendix-115 for "METHODS OF CONTRACEPTION"', 'role': 'assistant'}]