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共用题干 Plants in DesertOnly special plant

tikufree2019-12-17  22
问题 共用题干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℃．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.
选项 Ordinary plants are unable to survive in the desert mainly because of the changeable weather.A:Right B:Wrong C:Not mentioned
答案B
解析根据第一段第一句可知，只有特殊的植物才能在沙漠中存活，这是因为沙漠中土壤的温度过高，每年的温度能达到75℃以上，而并不是因为沙漠中的气候变化多端。 根据线索词“Grasses and flowers”和“see1seeas"，可以很快把第二段第一句确定为答案相关句。这个句子的大意是：沙漠里的花草年复一年以种子的形式度过漫长、炎热，而又干燥的季节。可见题干的说法与原文的说法一致，所以选择A项。 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。 本篇文章并未提到冬天里花草最难生存，所以选择C项。 利用题干中的“The shoot system”作为线索词，可以把第三段最后一句确定为答案相关句。这句话表明，茎轴系统极大地限制了蒸发所带来的水分损失，而不是说茎轴系统能减少植物对太阳光线的吸收。可见题干与原文的说法不符。 倒数第二段的主题句是第一句，讲述的主要是沙漠多年生植物能生存的原因。题干表述正确，所以选择A项。 根据题干中的线索词“lose their leaves1 "，不难把最后一段第一、二句确定为答案相关句。这两句话表明，沙漠多年生植物和较湿润地区的树木落叶的原因是一样的，都是为了减少水分的蒸发。
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