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
In an epidemic of plague, within 48 hours of application of insecticides by spraying the 'X' cheopis index should fall to - 
Select and explain. 
A. 1, B. 0, C. 2, D. 5
B: 0
Answer: B: 0 
Explanation: None