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  3. The concept of obtaining fresh water from icebergs that are pulled to populated areas and dry regions of the world was once trea

The concept of obtaining fresh water from icebergs that are pulled to populated areas and dry regions of the world was once trea

admin2013-05-19  8
问题     The concept of obtaining fresh water from icebergs that are pulled to populated areas and dry regions of the world was once treated as a joke more appropriate to cartoons than real life. But now it is being considered quite seriously by many nations, especially since scientists have warned that human race will outgrow its fresh water supply faster than it runs out of food.
    Glaciers are a possible source of fresh water that has been overlooked until recently. Three quarters of the Earth’s fresh water supply is still tied up in glacial ice, a reservoir of untapped fresh water so immense that it could sustain all the rivers of the world for 1,000 years. Floating on the oceans are 7,659 trillion metric tons of ice encased (包围) in 10,000 icebergs that break away from the polar ice caps, more than ninety percent of them from Antarctica.
    Huge glaciers that stretch over the shallow continental shelf give birth to icebergs throughout the year. Icebergs are not like sea ice, which is formed when the sea itself freezes; rather, they are formed entirely on land, breaking off when glaciers spread over the sea. As they drift away from the polar region, icebergs sometimes move mysteriously in a direction opposite to the wind, pulled by subsurface currents. Because they melt more slowly than smaller pieces of ice, icebergs have been known to drift as far north as 35 degrees south of the equator in the Atlantic Ocean. To corral them and steer them to parts of the world where they are needed would not be too difficult.
    The difficulty arises in other technical matters, such as the prevention of rapid melting in warmer climates and the funneling (通过漏斗般流过) of fresh water to shore in great volume. But even if the icebergs lost half of their volume in hauling, the water they could provide would be far cheaper than that produced by desalinating (融化海水), or removing salt from water.
What is the main topic of the passage?
选项 A、The movement of glaciers.
B、Icebergs as a source of fresh water.
C、Future water shortages.
D、The future of the world’s rivers.
答案B
解析 根据题干中的the passage将本题出处定位到全文。本文首先指出很多国家正在认真考虑obtaining fresh water from icebergs这一想法，接着说明冰川可以提供巨大的淡水资源，然后说明这一方法的可行性。由此可知，本文主要围绕从冰山中获取淡水资源展开，故答案为[B]。文章第三段提到冰山的运动是为了说明把冰山蓄拦起来并拖到世界上需要它们的地方将不会太困难，不是本文主要内容，故排除[A]；文章首段末句指出将来人类会面临淡水资源短缺，但文章讨论的重点不是缺水问题本身，而是如何用冰山来解决这一问题，故排除[C]。[D]是针对第二段设的干扰项。
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