Consider the following hypothetical scenario: An ancestral species of duck
had a varied diet that included aquatic plants and terrestrial plants and insects.
These ducks spent time on both land and water. Individuals of this species varied in
the amount of webbing in their feet, with some individuals having more webbing
and some having less. As many years went by, the environment changed such that
the aquatic food sources were much more plentiful than those on land. Many
generations later, almost all ducks had more webbing on their feet. How is this best
explained?

A. Ducks with less webbing worked harder than ducks with more webbing to eat aquatic plants. The more they used their feet, the more webbed their feet became, so they got enough food to survive and reproduce.

B. Due to chance mutations, all the ducks' feet in the next generation had more webbing. They were therefore able to eat aquatic plants and get enough food to survive and reproduce.

C. Ducks with more webbing were better at eating aquatic plants than ducks with less webbing, so the ducks with more webbing survived and reproduced better than ducks with less webbing.

D. Ducks with less webbing needed to grow more webbing in their feet in order to improve their access to aquatic plants, which allowed them to survive better and reproduce more.