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: Pharmacology
[{'content': 'Nonoxynol 9 ? \nSelect and explain. \nA. Is a chemical detergent, B. Is a barrier contraceptive, C. Can be used repeatedly in a day, D. Can be used to prevent STIs', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is'a'i.e., Is a chemical detergentNonoxynol - 9Chemical detergent that damages the sperm cell membranes, killing the cells.It is a safe, effective contraceptive option for women at low risk of HIV/ STIs", 'role': 'assistant'}]