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

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

admin2014-02-22  73
问题     The concept of obtaining fresh water from icebergs that are towed to populated areas and arid 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 the 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 every year are 7, 659 trillion metric tons of ice encased 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 of fresh water to shore in great volume. But even if the icebergs lost half of their volume in towing, the water they could provide would be far cheaper than that produced by desalinization, or removing salt from water.
It can be inferred from the passage that most icebergs______.
选项 A、become part of glaciers
B、drift toward the polar region
C、move in whichever direction the wind is blowing
D、melt in the oceans
答案D
解析 细节推断题。icebergs是从glaciers上断裂下来，选项A表达的正好相反，故不正确；由原文第三段第三句可知，icebergs是漂离the polar region，而不是漂向；同样是从原文第三段第三句的adirection opposite to the wind信息，可知冰山有时会在底层洋流的推动下颇为神秘地逆风移动，并不是whichever direction the wind is blowing；由原文尾段尾句icebergs lost half of their volume in towing可知，在拖的过程中冰山会失去一半体积。故答案为D。
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