What is the best indicator for a potential explosiveness of plague outbreak ?

Ans. is 'b' i.e., Cheopis index Flea indices o Flea indices are useful measurments of the density of fleas. o They are also useful in evaluating the efectiveness of a spraying programme. o The following indices are widely used in rat flea surveys : - i) Total flea index It is the average number of fleas of all species per rat. ii) Cheopis index --> It is the average number of X. cheopis per rat. It is a specific flea index, so it is a more significant index than total flea index. If this index is more than one, it is regarded as indicative of potential explosiveness of the situation, should a plague outbreak occur. iii) Specific percentage of fleas ---> It is the percentage of different species of fleas that are found on rats. iv) Burrow index ---> It is the average number of free - living fleas per species per rodent burrow.