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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  29
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.
How are icebergs formed?
选项 A、They break off from glaciers.
B、Seawater freezes.
C、Rivers freeze.
D、Small pieces of floating ice funneling.
答案A
解析 细节事实题。原文多处提到关键词icebergs，但结合关键词formed在原文重现的位置，可以确定答案在原文第三段第二句。分析原句的句子结构，判断they指代主句的主语Icebergs，当冰川伸展到海水中时，冰山就断裂下来。选项A中的break off与原文中的breaking off对应。故答案为A。
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