Why Did the Elimination of Wolves from Yellowstone National Park

Why did the elimination of wolves from Yellowstone National Park lead to a large reduction in the size of the aspen population?

A) Wolves and aspen are in a mutualistic relationship.
B) The absence of wolves led to large populations of elk,which consume the aspen.
C) The absence of wolves led to small populations of elk,and elk and aspen are in a mutualistic relationship.
D) The absence of wolves led to large populations of beavers,which consume the aspen.
E) Wolves and aspen are in a consumer-resource relationship.