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
Vector control for yellow fever around an airpo is done upto a distance of- 
Select and explain. 
A. 400m, B. 200m, C. 500m, D. 100m
A: 400m
Answer: A: 400m 
Explanation: Ans. is 'a' i.e., 400 m o Airpos and seapos are kept free from the breading of insect vectors over an area extending at least 400 meters around their peripeters.