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  3. One day, drought may be a thing of the past, at least in any country not too

One day, drought may be a thing of the past, at least in any country not too

游客2025-01-16  28
问题     One day, drought may be a thing of the past, at least in any country not too far from the sea. Vast areas of desert throughout the world may for the first time come to life and provide millions of hectares of cultivated land where now nothing grows.
    By the end of this century this may not be mere speculation. Scientists are already looking into the possibility of using some of the available ice in the Arctic and Antarctic. In these regions there are vast ice-caps formed by snow that has fallen over the past 50,000 years. Layer upon layer of deep snow means that, when melted, the snow water would be pure, not salty as sea-ice would be. There is so much potential pure water here that it would need only a fraction to turn much of the desert or poorly irrigated parts of the world into rich farmland. And what useful packages would come in! It should be possible to hack off a bit of ice and transport it! Alternatively perhaps a passing iceberg could be captured. They are always breaking away from the main caps and floating around, pushed by currents, until they eventually melt and are wasted.
    Many icebergs are, of course, much too small to be towed any distance, and would melt before they reached a country that needed them anywhere. It would be necessary to harness one that was manageable and that was big enough to provide a good supply when it reached us. Engineers think that an iceberg up to 11 kilometres long and 2 kilometres wide could be transported if the tug pulling it was as big as a supertanker! Even then they would cover only 32 kilometres every day. However, once the iceberg was at its destination, say at one end of Hong Kong harbour, more than 7,000 million cubic metres of water could be taken from it! That would probably be more than enough for Hong Kong even in the hottest summer! But no doubt a use could be found for it.
    Apparently, scientists say, there would not be too much wastage in such a journey. The larger the iceberg, the slower it melts, even if it is towed through the tropics. This is because when the sun has a bigger area to warm up, less heat actually gets into the iceberg. The vast frozen center would be unaffected.
    Even with the giant tug that would have to be available to tow an iceberg seven miles long, the voyage would take many months from the Antarctic to Hong Kong, for example, but as stronger engines are built and more is known about sea currents, the journey could get shorter and shorter and thus the wastage less and less. Airline pilots have learnt to use jet streams ten miles above the earth to increase speed and save fuel so, surely, a boat towing an iceberg could make use of fast-flowing currents and avoid warmer water.  [br] The main idea of the first paragraph is that______.
选项 A、much of desert has been changed into rich farmland already
B、the problem of drought could easily be solved all over the world
C、ice from the polar area may be used to solve the problem of drought
D、it is possible to solve the problem of drought in many countries
答案 D
解析 这是道主旨题，如果主旨题是第一题的话，考生不妨暂时放下，先做后面的，然后等最后看完了整篇文章再回来做，有时第一段或者最后一段会点出文章的主旨。有些需要通读全篇文章然后自己归纳。从文中可以看出在一些国家是可以解决干旱的问题。“Scientists are already looking into the possibility of using some 0f the available ice in the Arctic and Antarctic.”科学家已经在寻找利用北极和南极的冰川的可能性。故选D。
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