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  3. Plants in Desert Only special plants can survive the terrible climate of a desert, for these are regions where the annual ra

Plants in Desert Only special plants can survive the terrible climate of a desert, for these are regions where the annual ra

admin2014-05-13  25
问题                             Plants in Desert
    Only special plants can survive the terrible climate of a desert, for these are regions where the annual range of the soil temperature can be over 75 °C . Furthermore, during the summer there are few clouds in the sky to protect plants from the sun’ s ray. Another problem is the fact that there are frequently strong winds that drive small, sharp particles of sand into the plants, tearing and damaging them. The most difficult problem for all forms of plant life, however, is the fact that the entire annual rainfall occurs during a few days or weeks in spring.
    Grasses and flowers in desert survive from one year to the next by existing through the long, hot, dry season in the form of seeds. These seeds remain inactive unless the right amount of rain falls. If no rain falls, or if insufficient rain falls, they wait until the next year, or even still the next. Another factor that helps these plants to survive is the fact that their life cycles are short. By the time the water from the spring rains disappears—just a few weeks after it falls—such plants no longer need any.
    The perennials(多年生植物)have special features that enable them to survive as plants for several years. Thus, nearly all desert perennials have extensive root systems below ground and a small shoot system above ground. The large root network enables the plant to absorb as much water as possible in short time. The small shoot system, on the other hand, considerably limits water loss by evaporation(蒸发).
    Another feature of many perennials is that after the rainy season they lose their leaves in preparation for the long, dry season, just as trees in wetter climates lose theirs in preparation for the winter. This reduces their water loss by evaporation during the dry season. Then, in next rainy season, they come fully alive once more, and grow new branches, leaves and flowers, just as the grasses and flowers in desert do.
Grasses and flowers in the desert whose life cycles are short show their ability to adapt to the quick disappearance of rainwater there after it falls in spring.
选项 A、Right
B、Wrong
C、Not mentioned
答案A
解析 题干的大意是：沙漠里春季的雨水很快会消失，而沙漠里生命周期短的花草能够适应这一环境特点。利用题干中的“life cycles”作为线索词，可以很快把第二段第四、五句确定为答案相关句，这两句话表明，生命周期短能帮助植物在沙漠中存活，因为春季的雨水消失后，这些植物将不再需要雨水。可见题干的说法与原文的说法一致。
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