the use of pesticides on crops has been a common farming practice for decades. what had been the greatest effect of natural selection through the use of pesticides on certain insect populations?

yes? sounds right, but you didn’t ask a question.

most community's take hundreds of years to become stable

the correct answer is: b. pantala flavescens, because these organisms would have a high level of genetic variation due to sexual reproduction.  

because involves two organisms (parents) whose genetic material combines, sexual reproduction leads to genetic variation in new generations of offspring. the offspring is an unique organism, with new genome, more protected with the higher ability to adapted. this process is fundamental to evolution.