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 mushroom?
A. rough-legged hawk
B. barren-ground caribou
From the given choices, choose the correct answer and respond with the letter of that choice.

B