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  3. Large animals that inhabit the desert have evolved a number of adaptations for reducing the effects of extreme heat. One adaptat

Large animals that inhabit the desert have evolved a number of adaptations for reducing the effects of extreme heat. One adaptat

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问题     Large animals that inhabit the desert have evolved a number of adaptations for reducing the effects of extreme heat. One adaptation is to be light in color, and to reflect rather than absorb the Sun’s rays. Desert mammals also depart from the normal mammalian practice of maintaining a constant body temperature. Instead of trying to keep down the body temperature deep inside the body, which would involve the expenditure of water and energy, desert mammals allow their temperatures to rise to what would normally be fever height, and temperatures as high as 46 degrees Celsius have been measured in Grant’s gazelles. The overheated body then cools down during the cold desert night, and indeed the temperature may fall unusually low by dawn, as low as 34 degrees Celsius in the camel. This is an advantage since the heat of the first few hours of daylight is absorbed in warming up the body, and an excessive buildup of heat does not begin until well into the day.
    Another strategy of large desert animals is to tolerate the loss of body water to a point that would be fatal for non-adapted animals. The camel can lose up to 30 percent of its body weight as water without harm to itself, whereas human beings die after losing only 12 to 13 percent of their body weight. An equally important adaptation is the ability to replenish (Sheik) this water loss at one drink. Desert animals can drink huge volumes in a short time, and camels have been known to imbibe (吸收) over 100 liters in a few minutes. A very dehydrated person, on the other hand, cannot drink enough water to rehydrate at one session, because the human stomach is not sufficiently big and because a too rapid dilution of the body fluids causes death from water intoxication. The tolerance of water loss is of obvious advantage in the desert, as animals do not have to remain near a water hole but can obtain food from grazing sparse pastures. Desert-adapted mammals have the further ability to feed normally when extremely dehydrated, it is a common experience in people that appetite is lost even under conditions of moderate thirst.
What is the passage mainly about?
选项 A、Animals developed different strategies to survive.
B、Large animals can take strategies to reduce the effect of extreme heat.
C、Animals can tolerate the loss of body water.
D、A very dehydrated person can drink enough water to rehydrate.
答案A
解析 本文的主题句，即全文的中心思想在文章第一段的第一句“Large animals that inhabit the desert have evolved a number of adaptations for reducing the effects of extreme heat”因此本文讲的就是沙漠中的大型动物采用不同的策略来降低特别高的温度带来的副作用。因此A Animals developed different strategies to survive．动物采取不同的力．法生存与第一句话的意思比较相符。而选项B则说大动物能够消除过热带来的副作用，这句话就比较绝对。C Animals can tolerate the loss of body water．讲的是动物能够忍受身体缺水，这是动物适应环境的一个方面，因此我们不能以偏盖全，不能采用这个选项。同样的道理，我们也不能选D，它讲的是脱水的动物可以通过饮用大景的水来补水。因此我们选A。
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