This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Environment and health, Subject name: Social & Preventive Medicine
[{'content': 'According to WHO International Health organizations. What is the distance surrounding an Airpo or Seapo which should be free of mosquitoes? \nSelect and explain. \nA. 100 meter, B. 200 meter, C. 300 meter, D. 400 meter', 'role': 'user'}, {'content': "Answer: D \nExplanation: Under the WHO International Health Regulations, all international airpos and seapos are kept free from all types of mosquitoes for a distance of 400 m around the perimeter of the pos. Park's textbook of preventive and social medicine 23rd edition.", 'role': 'assistant'}]