This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Entomology, Subject name: Social & Preventive Medicine
Mosquito free airport perimeter: 
Select and explain. 
A. 400 m, B. 100 m, C. 200 m, D. 500 m
A: 400 m
Answer: A: 400 m 
Explanation: Ref: 21st edition Park, pg 259Explanation:India is a yellow fever receptive area - area in which yellow fever dose not exit, but where conditions would permit its development if introduced.As an international measure airports and seaports are kept free from the breeding of insect vectors over an area extending at least 400 meters around their perimeters.The aedes aegypti index' is kept below 1.