Peppered moths come in two color variations, as shown below.

Prior to the Industrial Revolution, the majority of the population in England consisted of the light colored variation. The dark colored moth became the dominant variation by the end of the 20th century and remained so for almost 100 years. Today, the light colored variation is dominant again.

What is the best explanation for this?

A.
A single variation can be beneficial under some conditions and harmful under other conditions.

B.
Populations with two variations have a better chance of survival than populations with more.

C.
One variation will always be harmful, and the other will always be beneficial.

D.
A single variation can be beneficial in all conditions or harmful in all conditions.