Refer to the figure.
In their work on aspen-fir interactions, Calder and St. Clair claim that aspens are facilitated by the presence of fir trees. From these data, what is the primary evidence for aspen being facilitated by fir?

A) Aspen mortality increases when they are within 0.5 m of a fir tree.
B) Fir mortality is highest when at distances greater than 0.5 m from aspen.
C) Aspen mortality decreases when they are within 0.5 m of a fir tree.
D) Aspen mortality is highest in fir-dominated stands.