TOEFL Reading: ETS-TOEFL阅读机经 - CGSCFV3C_4HA364FL$

Which of the following can be inferred from paragraph 3 about "North American sheep, elk, moose, musk ox, bears, antelope, and wolves" A. They have all changed as a result of hunting by humans. B. They all originated in North America at about the same time. C. They all contributed to the change in the bison's environment. D. They all contributed to the change in the bison's size and shape.