Antarctica has actually become a kind of space station a unique observation post for detecting important changes in the world's environment. Remote from major sources of pollution and the complex geological and ecological systems that prevail elsewhere, Antarctica makes possible scientific measurements that are often sharper and easier to interpret than those made in other parts of the world.

Growing numbers of scientists therefore see Antarctica as a distant-early-warning sensor, where potentially dangerous global trends may be spotted before they show up to the north. One promising field of investigation is glaciology. Scholars from the United States, Switzerland, and France are pursuing seven separate but related projects that reflect their concern for the health of the West Antarctic Ice Sheet a concern they believe the world at large should share.

The Transantarctic Mountain, some of them more than 14,000 feet high, divide the continent into two very different regions. The part of the continent to the "east" of the mountains is a high plateau covered by an ice sheet nearly two miles thick. "West" of the mountain, the half of the continent south of the Americas is also covered by an ice sheet, but there the ice rests on rock that is mostly well below sea level. If the West Antarctic Ice Sheet disappeared, the western part of the continent would be reduced to a sparse cluster of island.

While ice and snow are obviously central to many environmental experiments, others focus on the mysterious "dry valley"of Antarctica, valleys that contain little ice or snow even in the depths of winter. Slashed through the mountains of southern Victoria Land, these valleys once held enormous glaciers that descended 9,000 feet from the polar plateau to the Ross Sea. Now the glaciers are gone, perhaps a casualty of the global warming trend during the 10,000 years since the ice age. Even the snow that falls in the dry valleys is blasted out by vicious winds that roars down from the polar plateau to the sea. Left bare are spectacular gorges, rippled fields of sand dunes, clusters of boulders sculptured into fantastic shapes by 100-mile-an-hour winds, and an aura of extraterrestrial desolation.

Despite the unearthly aspect of the dry valleys, some scientists believe they may carry a message of hope of the verdant parts of the earth. Some scientists believe that in some cases the dry valleys may soak up pollutants faster than pollutants enter them.

1. What is the best title for this passage?

[A] Antarctica and environmental Problems.

[B] Antarctica: Earth's Early-Warning station.

[C] Antarctica: a Unique Observation Post.

[D] Antarctica: a Mysterious Place.

2. What would the result be if the West Antarctic Ice Sheet disappeared?

[A] The western part of the continent would be disappeared.

[B] The western part of the continent would be reduced.

[C] The western part of the continent would become scattered Islands.

[D] The western part of the continent would be reduced to a cluster of Islands.

3. Why are the Dry Valleys left bare?

[A] Vicious wind blasts the snow away.

[B] It rarely snows.

[C] Because of the global warming trend and fierce wind.

[D] Sand dunes.

4. Which of the following is true?

[A] The "Dry Valleys" have nothing left inside.

[B] The "Dry Valleys" never held glaciers.

[C] The "Dry Valleys" may carry a message of hope for the verdant.

[D] The " Dry Valleys" are useless to scientists.四级答案

答案详解

1. A 南极洲和环境问题。B. 南极洲：地球最早的报警战。C.南极洲：独一无二的观察哨。D. 南极洲：神秘的地方。三项都是总内容众的组成部分。

2. D 大陆西部成为一群岛屿。第三段“横断南极的山脉，有的高达一万四千多英尺，把这大陆分成情况各异的两个地区。山脉以东的大陆部分是由差不多两英里厚的冰层覆盖的高原;山脉以西，即美洲以南的半个大陆也为冰层所覆盖。可是，这里冰层覆盖在大大低于海平面的岩石。如果西南极洲冰层消失，那这大陆西部将成为稀疏的岛群。”A. 大陆西部将小时。B. 大陆西部缩小。 D. 大陆西部将成为分散的岛屿。

3. C 因为地球变暖和狂风劲吹。在第四段：“……这些干谷甚至在寒冬季节也很少有冰雪。它们插在南维多利亚陆地的山脉中，一度曾有从极地高原到罗斯海的深度为9000英尺的冰河。现在冰河已不存在，很可能是冰期之后一万年间地球变暖的结果。即使落入干谷的雪也被从极地高原咆哮入海的邪恶狂风吹散了。留下来的是裸露的壮观的峡谷，沙丘起伏的原野，被时速一百英里的大风雕刻成奇形怪状的大砾石，形成与世隔绝的荒凉景象。”A. 邪恶的狂风吹走了雪。B. 它很少下雪。D.沙丘。这三项只是干谷现象的一部分。

4. C 他们可能为地球上绿色地区带来了希望的信息。答案是第五段第一句“尽管干谷具有神秘的一面，科学家却相信他们可能为地球上葱绿的地方带来了希望的信息。”A.干谷内什么都没有留下。B. 干谷内从没有冰河。D. 按照科学家的看法，干谷毫无用处。