This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
[{'content': 'Vaccine which can be stored at - 10o c temperature - \nSelect and explain. \nA. Polio, B. Measles, C. BCG, D. DPT', 'role': 'user'}, {'content': 'Answer: A \nExplanation: .cold chai temerature for storage of OPV, routine storage -2 to 8 degree long term storage --20 to -40 degree ref:park&;s textbook,ed 22,pg no 57', 'role': 'assistant'}]