Mosquitoes Have Been Controlled in Most Parts of the World

Multiple Choice

Mosquitoes have been controlled in most parts of the world by the spraying of DDT.But after years of repeated sprayings,the number of mosquitoes has been increasing in spite of the continued use of DDT because:

A) each new generation of mosquitoes grew up with DDT as a part of the environment and gradually developed immunity
B) mosquitoes exposed to nonlethal concentrations of DDT learned to avoid food and other matters sprayed with DDT
C) DDT-resistant mosquitoes survived to breed,as did their offspring,until more and more of each year's mosquitoes were resistant
D) none of the above