A number of mosquito populations today are resistant to specific insecticides, even though those insecticides were highly effective when they were first introduced. Biologists believe that insecticide resistance evolved in mosquitoes because A. a few mosquitoes were probably resistant to the insecticide before it was ever used. These survived and passed that trait on to their offspring. B. mosquitoes needed to develop insecticide resistance to survive after the insecticide was used. C. the presence of the insecticide caused some mosquitoes to develop resistance; they survived and passed the trait to their offspring. D. current mosquito populations are phenotypically variable and exhibit differential fitness in different environments. E. individual mosquitoes built up an immunity to an insecticide after being exposed to it.

Rehashed utilization of a similar class of pesticides to control a bug can cause unwanted changes in the genetic stock of a vermin prompting another type of counterfeit determination, pesticide opposition. At the point when a pesticide is first utilized, a little extent of the bug populace may endure introduction to the material because of their unmistakable hereditary cosmetics
These people go along the qualities for protection from the people to come. Resulting employments of the pesticide increment the extent of less-helpless people in the populace. Through this procedure of choice, the populace step by step creates protection from the pesticide. Around the world, in excess of 500 types of bugs, bugs, and arachnids have built up some degree of pesticide opposition
Hence, the right answer is option "A"