Which statement best expresses the central idea of this article? a. ranchers do all they can to protect their sheep and cattle, even if it means killing off the wolves in the region. b. wolves are unlike many other predators because they do not guard or hide their prey but leave leftovers for other animals. c. wildlife biologists are concerned that animals that are taken out of an ecosystem will change its overall landscape. d. the wolves of yellowstone national park have shown that they are a species that other animals depend on in order to survive.