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': 'For the yellow fever control, distance around airport to be kept free of Aedes breeding is \nSelect and explain. \nA. 200m, B. 250m, C. 400m, D. 450m', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]