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Suppose we built a robot to explore the planet Mars. We provide the robot with seeing detectors(探测器) to keep it away from danger. It is powered entirely by the sun. Should we program the robot to be equally active at all the times? No. The robot would be using up energy at a time when it was not receiving any. So we would probably program it to stop its activity at night and to make up at dawn the next morning.
According to the evolutionary(进化的) theory of sleep, evolutionary equipped us with a regular pattern of sleeping and walking for the same reason. Theory does not deny(否认) That sleep provides some important restorative functions(恢复功能). It merely says that evolutionary has programmed us to perform those functions at a time when activity would be inefficient (无效的)and possibly dangerious. However, sleep protects us only from the sort of trouble we might walk into; it does not protect us from trouble that comes looking for us. So we sleep well when we are in a familiar, safe place, but we sleep lightly, if at all, when we fear that bears will nose into the tent.
The evolutionary theory explains the differences in sleep among creatures. Why do cats, for example, sleep so much, while horses sleep so little? Surely cats do not need five times as much repair and restoration as horse do. But cats can afford to have long periods of inactivity because they spend little time eating and are unlikely to be attacked while they sleep. Horse must spend over, they cannot afford to sleep to long or too deeply, because their survival(生存) depends on their ability to run away from attackers.
1.The author uses the example of the robot in space exploration to tell us ______.
A.the differences between robots and men
B.the reason why men need to sleep
C.about the meed for robots to save power
D.about the danger of men working at night
2.Evolution has programmed man to sleep at night chiefly to help him ______.
A.keep up a regular pattern of life
B.prevent trouble that comes looking for him
C.avoid danger and inefficient labour
D.restore his bodily functions
3.According to the author, we cannot sleep well when we_______.
A.are worrying about our safety
B.are overworked
C.are in a tent
D.are away from home
4.Cats sleep much more than horses do partly because cats _____________.
A.need more time for restoration
B.are unlikely to be attackers
C.are more active than horses when they are awake
D.spend less time eating to get enough energy
5.Which of the following is the main idea of the passage?
A.Evolution has equipped all creatures with a regular pattern of sleeping and waking
B.The study of the sleep is an important part of the evolutionary theory
C.Sleeping pattern must be taken into consideration in the designing of the robot
D.The sleeping pattern of a living creature is determined by the food it eats
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