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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

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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 (47)______ quite seriously by many nations, especially since scientists have warned that the human race will (48)______ its fresh water supply faster than it runs out of food.
    Glaciers are a possible (49)______ 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 (50)______ fresh water so immense that it could (51)______ 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 (52)______ 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 (53)______ 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 (54)______ 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 control them and (55)______ 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(传送) 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(脱盐), or (56)______ salt from water.

           Word Bank:
A. removing         I. approximately
B. stretch          J. considered
C. deriving         K. similar
D. entirely         L. source
E. untapped         M. ensured
F. resource         N. sustain
G. outgrow          O. steer
H. opposite
选项
答案J
解析 此处需要填入动词的过去分词与is being一起构成句子谓语。本句开头的But now表明该句与上文的…was once treated as…形成对比关系，因此该句的谓语意思与treat“认为”相近。由此可知词库中符合条件的过去分词为considered。
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