Now that man has actually landed on the surface of the moon, he has learned many new things about it. But one thing man knew before he ever reached the moon was that there was no life on it.
There is no atmosphere (大气层) on the moon. The lack of air means that the moon is not protected from any of the sun’s rays. The sun sends out heat and light radiation (辐射). Life on earth depends on heat and light. But the sun also sends out dangerous kinds of radiation. The earth’s atmosphere protects us from most of them. On the moon, however, there is no atmosphere to stop the radiation. All the sun’s rays beat down on the surface of the moon.
Because there is no atmosphere, the moon’s surface is either extremely hot or extremely cold. As the moon circles around the earth, the side of it that is lighted up by the sun becomes very hot. The temperature there reaches more than 300 degrees Fahrenheit (华氏温度). This is hotter than boiling water. The hot lunar
A. Why is there no air on the moon
B. Why is there no life on the moon
C. Why is the moon hotter than the earth
D. Why is the moon colder than the South Pole
Man has a big brain. He can think, learn and speak. Scientists used to think that man are different from animals because they can think and learn. They know now that animals--dogs, rats and birds--can learn. So scientists are beginning to understand that men are different from animals because they can speak. Animals cannot speak. They make noises when they are afraid, or hungry. or unhappy. Apes are our nearest cousins. They can understand some things mole quickly than human beings, and one or two have learned a few words. But they are still different from us. They cannot join words and make sentences. They cannot think like us because they have no language. They can never think about the past or the future. Language is a wonderful thing. Man has been able to develop civilization because he has language. Every child can. speak his own language vet well when he is four or five--but no animal learns to speak. How do children learn Scientists do not really know. What happens when w
A. animals cannot speak
B. animals cannot learn
C. animals cannot think like us
D. animals do not have their own language
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