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: Unknown
Indicator for outbreak of Plague epidemic is 
Select and explain. 
A. Rat burrow index, B. Total flea, C. Specific flea index, D. Cheopis index
D: Cheopis index
Answer: D: Cheopis index 
Explanation: “Cheopis index : It is an average no of X.cheopis per rat. It is a specific flea index. If this index is more than 1, it is regarded as indicative of potential explosiveness of the situation, should a plague outbreak occur”