During the Middle of the Twentieth Century, the Increased Elk

During the middle of the twentieth century, the increased elk population in the Greater Yellowstone Ecosystem led to a(n) _______ in the beaver population. The primary reason was that _______.

A) increase; elk were competing with beaver predators
B) increase; elk diseases were also affecting the beaver predators
C) decrease; elk diseases were also affecting beavers
D) decrease; elk were eating preferred food plants of the beavers