Part Ⅱ Reading Comprehension (35 minutes)

　　Directions: There are 4 passages in this part.Each passage is followed by some questions or unfinished statements.For each of them there are four choices marked A),B),C) and D).You should decide on the best choice and mark the corresponding letter on the Answer Sheet with a single line through the center.

　　Questions 21 to 25 are based on the following passage:

　　Some radio singals were heard in 1967.They were coming from a point in the sky where there was unknown star.They were coming very regularly,too:about once a second,if they were controlled by clock.

　　The scientists who heard the signals did not tell anybody else.They were rather afraid to tell in case they frightened people.The signals were coming from a very small body—no bigger,perhaps than the earth.Was that why no light could be seen from it?Or were the signals coming from a planet that belonged to some other star?There was no end to the questions,but the scientists kept the news secret.“Perhaps there are intelligent beings out there.”they thought,“who are trying to send messages to other planets,or to us?So the news was not given to the newspaper.Instead,the scientists studied the signals and searched for others like them...Well,all that happened in 1967 and 1968.Since then scientists have learnt more about those strange,regular,radio signals.And they have told the story,of course.

　　The signals do not come from a planet;they come from a new kind of star called a “pulsar””.About a hundred other pulsars have now been found,and most of them are very like the first one.

　　Pulsars are strong radio stars.They are the smallest but the heaviest stars we know at present.A handful of pulsar would weigh a few thousand tons.Their light—if they give much light—is too small for us to see.But we can be sure of this,no intelligent beings are living on them.

　　21. The radio signals discussed in this passage____.

　　A.were regular B.were controlled by a clock

　　C.were heard in 1967 only D.were secret messages

　　22. The radio singals were sent by____.

　　A.a satelliteB.a planet

　　C.a sky body which was unknown at that time

　　D.intelligent beings who were unknown at that time

　　23. The scientists did not tell people about the signals because____.

　　A.the singals stood for secret messages

　　B.people would ask them too many questions

　　C.they did not want to frighten people

　　D.they stood for unimportant messages

　　24. A pulsar is____.

　　A. a small heavy star which sends out strong radio signals and cannot be seen

　　B. a small heavy planet which sends out strong radio signals and cannot be seen

　　C. a small heavy satellite which sends out strong radio signals and cannot be seen

　　D. a small intelligent being who sends out strong radio signals and cannot be seen 25. Which of the following is true?

　　A.One of the pulsars found by scientists sends radio signals.

　　B.Pulsar began to send radio singals in 1967.

　　C.Scientists have searched for pulsars for many years but found none.

　　D.Scientists have found many pulsars since 1967.

　　Questions 26 to 30 are based on the following passage:

　　Over vast areas of every continent,the rainfall and vegetation necessary for life are disappearing.Already more than 40 percent of the earth's land is desert or desertlike.About 628 million people—one out of seven—live in these dry regions.In the past,they have managed to survive,but with difficulty.[ZZ(Z]Now largely through problems caused by modern life,their existence is threatened by the slow,steady spread of the earth's deserts.

　　Scientists still do not understand all the complex problems of the desert,but there have been many ideas for saving the land.Sandi Arabia has planted 10 million trees to help keep the sand from taking over fertile areas.The Israelis are aga in using some of the water collection systems left by the ancient people in the Negev desert.They plan to water their orchards with the extra water.Some Sahel farmers still raise cattle on their poor farm land,but before the cattle are sold,they are taken to greener lands in the south to get fat.

　　26. What is the article mainly concerned?

　　A.The problem of spreading desert.

　　B.The rainfall and vegetation in desert areas.

　　C.The water collection systems.

　　D.The difference between modern life and ancient life.