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': 'Which is not true about Yellow fever \nSelect and explain. \nA. Exotic, B. Incubation period 2-6 days, C. Live Attenuated 17 D strain vaccine, D. Validity of vaccine 6 years', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]