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Polar Bears spend most of their time on the sea ice in search of seals. And seals spend most of their time under that ice, avoiding the top predator. But climate change is giving polar bears additional challenges in their searches for food.

“Sea ice is now drifting(漂流) faster,” said George Durner. He and his colleagues compared sea ice conditions from 1987 to 1998 with those from 1999 to 2013. “And what we found was that ice drift at the locations used by polar bears increased 30% in the Beaufort sea and 37% in the Chukchi sea.” That’s a problem because polar bears are homebodies—they prefer to stay in a specific range. “Throughout their range, they seem to have a sense of place. And here we have a situation where the general pattern of ice drift is westward, so to remain in your traditional range, it means you have to constantly be walking eastward to compensate(抵消) for that westward drift.”

The result is a large-scale polar bear treadmill. And all that walking requires extra fuel. On average, a single bear eats between 31 and 33 seals per year. But the metabolic consequence of the treadmill effect means they have to eat on average one to three more. The study is in the journal Global Change Biology. And not only is the ice drifting faster, it’s also melting more, giving the bears less of the platform they use to pursue their prey(猎物). So they need more seals but have a tougher time to track them. All put polar bears on a slippery slope.

1.The underlined word “predator” means ______ in Chinese.

A 人类

B 捕食者

C 猎人

D 机器

解析：选B。词义猜测题。海豹大部分时间都待在海冰下，躲避冰上的捕食者(predator)，故选B。

2.Ice drift increased _____ from 1999 to 2013 in the Chukchi sea.

A 30%

B 33%

C 35%

D 37%

解析：选D。细节理解题。根据第二段And what we found was ice drift at the locations used by polar bears increased 30% in the Beaufort sea and 37% in the Chukchi sea.可知，故选D。

3.Polar bears are homebodies, and they prefer to stay in a ______ range.

A big

B special

C specific

D smaller

解析：选C。细节理解题。根据第二段That’s a problem because polar bears are homebodies—they prefer to stay in a specific range. 可知，故选C。

4.Which of the following statements is NOT true?

A Sea ice is now drifting more and more slowly.

B Polar bears are homebodies.

C Ice drift at the locations used by polar bears increased 30% in the Beaufort sea.

D On average, a single bear eats between 31 and 33 seals per year.

解析：选A。细节理解题。A与第二段第一句Sea ice is now drifting faster不符，故选A。

5.What’s the best title of this passage?

A Climate change makes polar bears treadmill.

B Climate change is good for polar bears.

C Sea ice is now drifting faster.

D Polar bears are homebodies.

解析：选A。文章标题题。本文主要介绍了气候变化导致北极熊的处境越来越糟糕，故选A。