Over the Past Century, Sagebrush Has Dramatically Expanded Its Range

Over the past century, sagebrush has dramatically expanded its range over the Colorado plateauʹs grasslands. This development has been attributed to the overgrazing of the areaʹs grasses by cattle and sheep. This example indicates that

A) the relationship between sagebrush and grasses is mutualistic.
B) sagebrush could not exist anywhere in the absence of cattle and sheep.
C) grazing has no effect on the distribution of plants.
D) sagebrush is the dominant competitor over grasses.
E) the range of sagebrush is normally limited by competition with grasses.