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': 'All are true about measles except - \nSelect and explain. \nA. Incubation period is 10-14 days, B. Secondary attack rate is 30-40%, C. Sub cutaneous vaccine is available, D. Vaccine is live attenuated', 'role': 'user'}, {'content': 'Answer: B \nExplanation: SAR of measles is approximately 80%.', 'role': 'assistant'}]