阅读理解。 Suppose we built a robot to explore the planet Mars.We provide the robot with seeing dete

阅读理解。 Suppose we built a robot to explore the planet, Mars.We provide the robot with seeing detector (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 time？ 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 wake up at dawn the next

morning.

According to the evolutionary (进化的) theory of sleep, evolution equipped us with a regular pattern

of sleeping and waking for the same reason.The theory doesn"t deny that

sleep provides some important restorative functions. It merely says that evolution has programmed us to

perform those functions at a time when activity would be inefficient and possibly dangerous. However,

sleep protects us only from the sort of trouble we might walk into; it doesn"t protect us from trouble that

comes looking for us. So we sleep well when we are in a familiar and 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 instance,

sleep so much,while horses sleep so little？ Surely cats do not need five times as much repair and

restoration as horses do.But cats can afford to have long periods of inactivity because they spend little

time eating and unlikely to be attacked while they sleep. Horses must spend almost all their waking hours

eating, because what they eat is very low in energy value. Moreover,they cannot afford to sleep too long

or too deeply, because their survival depends on their ability to run away from attackers.

1.The author used 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 need for robots to save energy

D.about the danger of men working at night

2. Evolution has programmed man to sleep at night mainly to help him _____.A. avoid danger and ineffective labor

B. restore his bodily functions

C. prevent trouble that comes looking for him

D. keep up a regular pattern of life

3. Cats sleep much more than horses do partly because they _____.A. are more active than horses when they"re awake

B. need more time for restoration

C. spend less time eating to get enough energy

D. are unlikely to be attackers

4.Which of the following is the main idea of the passage？A. The study of sleep is an important part of the evolutionary theory.

B. The sleeping pattern of a living creature is determined by the food it eats.

C. Sleeping patterns must be taken into consideration in the designing of robots.

D. Evolution has equipped all creatures with a regular pattern of sleeping against waking.