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': 'Sterility is caused by : \nSelect and explain. \nA. Vinca alkaloids, B. Alkylating agents, C. Antimetabolites, D. Actinomycin D', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]