After years of heated debate, gray wolves were reintroduced to Yellowstone National Park. Fourteen wolves were caught in Canada and transported to the park. By last year, the Yellowstone wolf population had grown to more than 170 wolves.
Gray wolves once were seen here and there in the Yellowstone area and much of the continental United States, but they were gradually displaced by human development. By the 1920s, wolves had practically disappeared from the Yellowstone area. They went farther north into the deep forests of Canada, where there were fewer humans around.
The disappearance of the wolves had many unexpected results. Deer and elk populations — major food sources (来源) for the wolf — grew rapidly. These animals consumed 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 of the park’s red foxes, and completely drove away the park’s beavers.
As early as 1966, biologists asked the government to consider reintroducing wolves to Yellowstone Park. They hoped that wolves would be able to control the elk and coyote problems. Many farmers opposed the plan because they feared that wolves would kill their farm animals or pets.
The government spent nearly 30 years coming up with a plan to reintroduce the wolvers. The U.S. Fish and Wildlife Service carefully monitors and manages the wolf packs in Yellowstone. Today, the debate continues over how well the gray wolf is fitting in at Yellowstone. Elk, deer, and coyote populations are down, while beavers and red foxes have made a comeback. The Yellowstone wolf project has been a valuable experiment to help biologists decide whether to reintroduce wolves to other parts of the country as well.

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1.What is the text mainly about?

A Wildlife research in the United States.

B Plant diversity in the Yellowstone area.

C The conflict between farmers and gray wolves.

D The reintroduction of wolves to Yellowstone Park.

解析：选D。主旨大意题。根据全文可知，文意开门见山地提出黄石公园引进灰狼的举措，然后在下文中详细介绍其原因以及带来的良好的转机，由此判断本文的中心话题是美国黄石公园对灰狼的引进，故选D。

2.What does the underlined word “displaced” in paragraph 2 mean?

A Tested.

B Separated.

C Forced out.

D Tracked down.

解析：选C。词义猜测题。根据第二段最后两句By the 1920s, wolves had practically disappeared from the Yellowstone area. They went farther north into the deep forests of Canada, where there were fewer humans around.可知，因为人类的发展，侵占了灰狼的领域，灰狼逐渐向北迁徙，由此推断灰狼被人类排挤走了，故选C。

3.What did the disappearance of gray wolves bring about?

A Damage to local ecology.

B A decline in the park’s income.

C Preservation of vegetation.

D An increase in the variety of animals.

解析：选A。推理判断题。根据第三段的内容可知，灰狼的减少造成了鹿群的增多，植被遭到了破坏；郊狼数量的快速增长，它们猎杀了大量的赤狐，赶走了河狸，由此可推断出灰狼的消失导致了当地生态平衡被破坏，故选A。

4.What is the author’s attitude towards the Yellowstone wolf project?

A Doubtful.

B Positive.

C Disapproving.

D Uncaring.

解析：选B。观点态度题。根据文章最后一段最后一句The Yellowstone wolf project has been a valuable experiment to help biologists decide whether to reintroduce wolves to other parts of the country as well.可知，作者认为引进灰狼的项目是很有价值的尝试，因此可推知作者对这一举措持肯定的态度，故选B。