Which term best describes the change from more light-colored moths to more dark-colored moth

During the Industrial revolution, due to pollution, trees become darker in the urban area. Light-colored moths were, thus, easy prey. The dark-colored moths were able to camouflage on dark trees and avoid predators. The phenomenon is known as industrial melanism. So, in polluted urban areas, the number of dark-colored peppered moths increased. In the clean environment, were much effective in hiding from predators and they outnumbered the dark-colored moths. 

i thinking chemical change

d. planting trees

the trees take in carbon to make oxygen.