Which of the Following Would Be an Example of Directional

Which of the following would be an example of directional selection?

A) Mutations change the gene frequency of a population.
B) All of the plants on an island are killed by a volcanic eruption.
C) In a forest, the taller oak trees produce twice as many acorns as shorter ones.
D) Mice that were painted with a white stripe by biologists were eaten by predators more often than those that were not painted