After years of heated debate, gray wolves werereintroduced to Yellowstone National Park. Fourteen wolves were caught inCanada and transported to the park. By last year, the Yellowstone wolfpopulation had grown to more than 170 wolves.
Gray wolves once were seen here and there in theYellowstone area and much of the continental United States, but they weregradually displaced by human development. By the 1920s, wolves hadpractically disappeared from the Yellowstone area. They went farther north intothe deep forests of Canada, where there were fewer humans around.
The disappearance of the wolves had many unexpectedresults. Deer and elk populations — major food sources (来源) for the wolf — grew rapidly. These animalsconsumed large amounts of vegetation (植被), which reduced plant diversity in the park. In the absence of wolves,coyote populations also grew quickly. The coyotes killed a large percentage ofthe park’s red foxes, and completely drove away the park’s beavers.
As early as 1966, biologists asked the government to considerreintroducing wolves to Yellowstone Park. They hoped that wolves would be ableto control the elk and coyote problems. Many farmers opposed the plan becausethey feared that wolves would kill their farm animals or pets.
Thegovernment spent nearly 30 years coming up with a plan to reintroduce thewolvers. The U.S. Fish and Wildlife Service carefully monitors and manages thewolf packs in Yellowstone. Today, the debate continues over how well the graywolf is fitting in at Yellowstone. Elk, deer, and coyote populations are down, whilebeavers and red foxes have made a comeback. The Yellowstone wolf project hasbeen a valuable experiment to help biologists decide whether to reintroducewolves to other parts of the country as well.
（28）What is the textmainly about?A. Wildlife research in the United States.B. Plant diversity inthe Yellowstone area.C. The conflict between farmers and gray wolves.D. Thereintroduction of wolves to Yellowstone Park.
（29） What doesthe underlined word ＂displaced＂ in paragraph 2mean?A. Tested. B. Separated.C. Forcedout. D. Tracked down.
（30）What did thedisappearance of gray wolves bring about?A. Damage to local ecology. B. Adecline in the park’s income.C. Preservation of vegetation. D. An increase in thevariety of animals.
(31) What is the author’s attitude towards theYellowstone wolf project? A. Doubtful. B. Positive. C. Disapproving. D. Uncaring.