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': 'What is the recommended duration of quarantine for yellow fever? \nSelect and explain. \nA. 3 days, B. 6 days, C. 9 days, D. 12 days', 'role': 'user'}, {'content': 'Answer: B \nExplanation: A traveller should be placed in a mosquito proof ward for 6 days from the date of leaving an infected area. Ref: Park 21st edition, page 259.', 'role': 'assistant'}]