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 requires the most stringent conditions for storage \nSelect and explain. \nA. DPT, B. OPV, C. BCG, D. TT', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Among the vaccines, polio is the most sensitive to heat, requiring storage at minus 20 degree Celsius. Vaccines which must be stored in the vaccine compaments are polio and measles. The cold chain is a system of storage and transpo of vaccines at low temperature from the manufacturer to the actual vaccination site (refer pgno:109 park 23 rd edition)', 'role': 'assistant'}]