Assertion (A) : The number of white winged moths decreased drastically after industrialization in England.

Reason (R) : Effects of industrialization were more marked in rural areas of England.

The correct option is: Assertion (A) is true, but Reason (R) is false.

Explanation of Assertion (A):
Before the onset of industrialization in England (prior to the 1850s), tree trunks were covered with light-colored lichens. The light-colored or white-winged moths (Biston betularia) were well-camouflaged against these trunks, protecting them from predatory birds. Meanwhile, dark-colored (melanic) moths were easily spotted and preyed upon.
However, after industrialization, heavy coal smoke and soot deposition blackened the tree trunks and killed the lichens. Consequently, the white-winged moths lost their camouflage and became highly vulnerable to predators, leading to a drastic decrease in their population. Meanwhile, the dark-winged moths survived and increased in number. Therefore, Assertion (A) is true.

Explanation of Reason (R):
The effects of industrialization, such as soot accumulation and pollution, were highly concentrated in urban and industrial centers rather than rural areas. In rural and non-industrialized areas, the tree trunks remained clean and covered with lichens, allowing the white-winged moths to maintain a higher population density. Thus, the effects of industrialization were more marked in urban/industrial areas, making Reason (R) false.