Apply: adaption and environmental change

A population of snails lives in a forest habitat where they have several predators, including birds and small mammals. The snails have shells that can be either light, medium, or dark brown in color.

The number of individuals in the population with each shell color is shown in the following graph.

The snails’ forest habitat has experienced several years of heavier-than-normal rainfall. As a result, the top layer of dark soil has eroded away and exposed a layer of lighter colored rock.

Given this environmental change, which of the following graphs represents the most likely distribution of shell color in the snail population after enough time has passed for natural selection to occur?