Context: Below is a food web from a tundra ecosystem in Nunavut, a territory in Northern Canada.
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.
In this food web, which organism contains matter that eventually moves to the earthworm?
A. Arctic fox
B. mushroom
C. grizzly bear
D. lichen
Answer with the option's letter from the given choices directly.

A