On the Slopes of the Washington Cascades, Ecologists Have Studied

On the slopes of the Washington Cascades, ecologists have studied some closely related vole species for decades. Many of these vole species, when they occur on separate mountains, tend to choose very similar food sizes. However, when these species occur together on the same mountain slope, their food choices tend to differ, with some species selecting small seeds and others feeding exclusively on larger seeds. This behavior may be an example of:

A) niche fragmentation.
B) resource partitioning.
C) habitat fragmentation.
D) intraspecific competition.
E) intraspecific range diversion.