Context: Below is a food web from Shenandoah National Park, a forest ecosystem in Virginia.
A food web models how the matter eaten by organisms moves through an ecosystem. The arrows in a food web represent how matter moves between organisms in an ecosystem.
Which of the following organisms is the omnivore in this food web?
A. silver maple
B. beaver
C. gray fox
D. pine vole
Select the correct answer from the provided options and reply with the letter associated with it.

D