Answer:
Natural selection.
Step-by-step explanation:
The dark colour butterflies will increase in their population due to favourable conditions of the surrounding environment. They are naturally selected by the nature due to their suitability and compatibility with the environment that allows dark butterflies to increase in their population. The colour of dark butterflies helps them to not eaten by the predators that allows them to increase in their population so we can say that this type of selection is natural selection.