A．It is noisy. B．It is smelly.

　　C．It is starving D．It has good eyesight.

　　解析：选C　细节理解题。由第四段中的"In a moment it is over, and the bear eats his first meal in nearly a week"可知，这只白熊很饿。

　　2．What do we know about polar bears' ancestors?

　　A．They were a darker­colored species.

　　B．They were born to live in ice and snow.

　　C．They had no trouble getting used to the icy north.

　　D．They came to the Arctic Ocean about 1,000 years ago.

　　解析：选A　细节理解题。由第五段中的"Polar bears rule the frozen sea, but their ancestors (祖先) weren't always built for ice and snow. The first Arctic bears were brown bears, a species that includes grizzly bears"可知，北极熊的祖先皮毛颜色更深一些。

　　3．Why are polar bears struggling to survive?

　　A．They are losing their hunting ground.

　　B．They are threatened by other animals.

　　C．They are spending little time on land.

　　D．They have difficulty reaching the shore.

　　解析：选A　推理判断题。由倒数第二段中的"Sadly, these characteristics may now threaten the polar bear's survival. As sea ice melts due to global warming, polar bears are frequently forced to come ashore"可知，随着气温上升，北极熊狩猎的海水冰面消失，使得它们的生存面临威胁。

　　4．Which of the following can be the best title for the text?

　　A．The climate change

　　B．The polar bear's favorite meal

　　C．The dark past of the polar bear

　　D．The mysteries of the Arctic Ocean

　　解析：选C　标题归纳题。文章讲到北极熊的祖先毛皮颜色更深，C项中的The dark past 既表明了北极熊祖先的外表特征，也暗含它们过去误入北极的历史。

　　B

Migrations are one of the animal kingdom's most widespread phenomena. They are seasonal tests of endurance, collective journeys often taken at great costs by birds, whales, land mammals, insects, and other creatures that are wired to travel. Scientists estimate that one third to half of all animals - and even some microorganisms - migrate during part of their lives.