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: Social & Preventive Medicine
[{'content': 'After reconstitution, the vaccine must be stored in the dark at 2-8 degree C and used within: September 2004 \nSelect and explain. \nA. 1 hour, B. 2 hours, C. 3 hours, D. 6 hours', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. D i.e. 6 hour Reconstituted measles vaccine loses about 50% of its potency after 1 hour at 20 degree C; it loses almost all potency after 1 hour at 37 degree C.', 'role': 'assistant'}]