In the past, man did not have to think about the protection of his environment．There were few people on the earth, and natural resources seemed to be enough.

　　 Today things are　 36　 , the world has become too crowded. We are using up our natural resources too quickly and at the same time we are polluting our environment with dangerous chemicals. If we keep doing this, human life on the earth 　 37　 survive(生存）.

　　 Everyone realizes today that if 　 38　 fishes are taken from the sea, there will soon be none left. Yet, with modern fishing ways, more and more fishes are caught. We know that if lots of trees are cut down, forests will disappear and nothing will grow on the earth. Yet we　 39　 to use bigger and more powerful machines to cut down trees.

　 We realize that if rivers 　 40　 with waste products from factories, fish will die.　 41　 , in most countries wastes are still put into rivers or into the sea.

We know, too, that if the　 42　 of the world keep on rising at the present rate, in a few years there will not be enough food. What can we do to solve these problems? If we eat 　 43　 , there will be more food for everyone．Land that is used to grow crops feeds　 five times more people than land where animals are kept．

　 Our natural resources will　 44　 longer if we learn to recycle them．

　 Finally, if we educate people to think about the problems, we shall have a better and cleaner　 45　 in the future.

36. A. common 　　B. the same 　　C. changeable 　　D. different

37. A. may not 　　B. will not 　　 C. shall not 　　　 D. could not

38. A. too many　　 B. many too　　 C. too much　　　 D. much too

39. A. continue 　　B. have 　　　C. ought 　　　D. decide

40. A. pollute　　 　B. will pollute　 　C. are polluted 　　　D. are polluting

41. A. And 　　　　B. However 　　　C. Generally 　　　D. Therefore

42. A. production 　　B. pollution 　　 C. population 　　D. Development

43. A. more vegetables and less meat　　　 B. less vegetables and more meat

　 C. more vegetable and more meat　　　 D. less vegetable and less meat

44. A. use 　　 B. stay 　　　C. keep 　　　 D. last

45. A. nature 　　　B. sea 　　 C. planet 　　　D. forest

In the summer of 1978 an English man named Steven was driving his tractor through a field of wheat when he discovered something strange. Some of his wheat was lying on the ground. The flattened wheat formed(形成)a circle about six meters across . Around this circle were four smaller circles of flattened wheat.
　 Three years later a farmer who lived nearby discovered almost the same circles in one of his fields. These circles were larger—nearly 15 meters across . That same year , another English farmer discovered three circles of flattened wheat on his land—one large circle between two small circles. During the following years, farmers in England found circles in their fields more and more often.
　 The circles are called “crop circles” because they usually appear in fields of wheat or corn. The wheat in the circles lies on the ground but is never broken; it keeps on growing, and the farmers can later harvest it. Farmers always discover the crop circles in the morning, so the circles probably form at night. They appear only in the months from May to September. What causes the crop circles?
　 At first, people thought that some kids were making them as a joke, or that farmers were making them to attract tourists.(In fact, in 1991, two men said they made the circles themselves, but many scientists don’t believe them.) People tried to copy them: They tried to make circles exactly like the ones the farmers had found. They couldn’t do it. They couldn’t enter a field of wheat without leaving tracks, and they couldn’t flatten the wheat without breaking it.
　 Several times people reported seeing stranger objects near the fields where crop circles later appeared. Many people believe that these crop circles are the messages sent by living things from outer space(外层空间)or the marks left by their spaceships.
　 Scientists who have studied the crop circles try to find out what causes them. In the summer of 1990 some scientists spent three weeks in the part of England where many circles have appeared. They had all the latest high-tech equipment(最新高科技设备). The equipment—worth 1.8 million dollars—got nothing. But one night, as the scientists were watching a field, crop circles formed in the field behind them, which were quite different from the others. The scientists had neither seen nor heard anything.
　 When Steven discovered the crop circles on his land in 1978, he said, “It was just like something that had landed in the field from the air and gone back up again. I don’t know what to make of these things.”
　 Crop circles have appeared in England, Japan, the United States and Russia. Experts from all over the world have studied them, and they say what Steven said: They don’t know what to make of these things.
【小题1】Which picture is probably the one formed in the field behind the scientists?

【小题2】“Flattened wheat” means ___________.
　　  

A．broken wheat

B．lying wheat

C．harvested wheat

D．growing wheat

【小题3】The passage is mainly about something ___________ .

A．that is done by living things from outer space

B．that cannot be solved but found all around the world

C．that cannot be made clear or understood

D．that is discovered and copied by the farmers