State one possible reason that the light colored variety was not completely eliminated from the polluted environment answer

Perhaps those light colored moths had other characteristics that allowed them to escape the predators. Additionally, there is variety in a species and additional white moths might still be born. Larger number of the dark-colored variety were present in the polluted environment because the dark colored moths would blend in with the polluted trees and therefore be camouflaged for survival. 

The answer is b. hope this !