B
As a result of pollution, Lake Erie, on the borders of the USA and Canada, is now without any living things.
Pollution in water is not simply a matter of “poisons” killing large numbers of fish overnight, Very often the effects of pollution are not noticed for many months or years because the first organisms（生物体）to be affected are either plants or plankton(浮游生物). But these organisms are the food of fish and birds and other creatures. When this food disappears, the fish and birds die too. In this way a whole food chain can be wiped out, and it’s not until dead fish and water birds are seen at the river’s edge or on the seashore that people realize what is happening.
　　Where do the substances which pollute the water come from? There are two main sources of sewage（下水道污物）and industrial waste. As more detergent（洗涤剂）is used in the home, so more of it is finally put into our rivers, lakes and seas. Detergents harm water birds, dissolving the natural substances which keep their feathers water-proof (防水). Sewage itself, if not properly treated, makes the water dirty and prevents all forms of life in rivers and the sea from receiving the oxygen they need. Industrial waste is even more harmful as there are many highly poisonous things in it, such as copper and lead.
　　So, if we want to stop this pollution, the answer is simple: sewage and industrial waste must be made clear before flowing into the water. It may already be too late to save some rivers and lakes, but others can still be saved if the correct action is taken at once.
70. Pollution of water is noticed________.
　　A. when the first organisms are affected　     
B. when a good many fish and birds die
　　C. when poisonous things are poured into water　
D. as soon as the balance of nature is destroyed
71.The living things die because there is no ________in the lake or river.
　　A. water　　　　　            B. fish           　 C. poison　　　　　  D. oxygen
72. Which of the following is harmful according to the passage?
　　A. Organisms              　B. Plants and plankton in the water
　　C. Waste water from cleaning    D. Industrial waste made clear before flowing into the water
73. The way to stop water pollution is to________.
　　A. realize the serious situation clearly
　　B. put oxygen into the river
　　C. make the waste material harmless before flowing into the water
　　D. make special room in the sea for our rubbish

完形填空：阅读下面短文，掌握其大意，然后从各题所给的四个选项中选出一个最佳答案。（共20小题，每小题1.5分）

   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　46　 .                    Today things are　 47　 , the world has become too　 48　 . We are using up our natural resources too quickly, and at the same time we are　 49　 our environment with dangerous chemicals. If we continue to do this, human life on the earth　 50　 survive.

　　Everyone　51　 today that if too many fish are taken from the sea, there will soon be none left. Yet, with modern fishing　 52 , more and more fish are caught. We know that if too many trees are cut down, 　53　 will disappear and nothing will grow on the land. Yet, we　 54　 to use bigger and more powerful machines to　 55　 more and more trees.

　　We realize that if rivers are polluted with waste products from factories, we will die.　 56　 , in most countries wastes are　 57　 put into rivers or into the sea, and there are　 58　 laws to stop this. We know, too, that if the　 59　 of the world continues to rise at the present rate, in a few years there will not be enough 60　. What can we do to solve these problems ?

　  If  we eat more vegetables and less　 61　 , there will be more food available for everyone. Land that is used to grow crops　 62　 five times more people than land where animals are kept. Our natural resources will　 63　 longer if we learn to recycle them. The world population will not rise so quickly if people use modern methods of birth 64　 .

　　Finally, if we educate people to think about the problems, we shall have a better and clearer 65　 in the future.

A. beautiful         B. unlimited          C. rare                  D. valuable

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

A. crowded         B. small                C. dirty                 D. busy

A. protecting       B. saving            C. polluting           D. fighting

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

A. wonders         B. realizes             C. consider            D. discovers

A. poles              B. boats                 C. methods            D. ideas

A  mountains     B. the sea                  C. trees                 D. forests

A. continue         B. have                 C. ought                D. go on

A. grow            B. plant                 C. save                  D. cut down

A. Thus       B. However     

C. Generally speaking  D. Therefore

A. still                     B. even                 C. also                  D. certainly

A. too many      B. a few                C. some                 D. few

A. production    B. pollution           C. population      D. revolution

A. houses          B. vegetables      C. food                 D. lives

A. fruit             B. meat                 C. fish                   D. grain

A. feeds            B. increases           C. supplies             D. helps

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

A. control         B. born                 C. plan                  D. reward

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

完形填空：阅读下面短文，掌握其大意，然后从各题所给的四个选项中选出一个最佳答案。（共20小题，每小题1.5分）
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　46　.                    Today things are　 47　 , the world has become too　 48　 . We are using up our natural resources too quickly, and at the same time we are　 49　 our environment with dangerous chemicals. If we continue to do this, human life on the earth　 50　 survive.
　　Everyone　51　 today that if too many fish are taken from the sea, there will soon be none left. Yet, with modern fishing　 52 , more and more fish are caught. We know that if too many trees are cut down, 　53　 will disappear and nothing will grow on the land. Yet, we　 54　 to use bigger and more powerful machines to　55　 more and more trees.
　　We realize that if rivers are polluted with waste products from factories, we will die.　 56　 , in most countries wastes are　 57　put into rivers or into the sea, and there are　 58　 laws to stop this. We know, too, that if the　 59　of the world continues to rise at the present rate, in a few years there will not be enough 60　. What can we do to solve these problems ?
　  If  we eat more vegetables and less　 61　 , there will be more food available for everyone. Land that is used to grow crops　 62　 five times more people than land where animals are kept. Our natural resources will　 63　 longer if we learn to recycle them. The world population will not rise so quickly if people use modern methods of birth 64　 .
　　Finally, if we educate people to think about the problems, we shall have a better and clearer 65　in the future.

We shall not drown if we remember these rules:

1. Never 　　 swim alone.
2. Never 　　 swim at a beach if there is no lifeguard.
3. Never 　　 swim after a meal or when you feel hungry.
4. Never 　　 rely on rings, floats or other swimming aids. You may lose them or they 　　 may let you sink.
5. Do 　　 not stay in the water too long, especially if it is cold.
6. Before 　　 you dive, be sure that the water is deep enough and that you will not hit 　　 anybody.
7. Never 　　 go out in a boat if you can’t swim or if you are not wearing a life 　　 jacket.

If you fall into difficulty, this is that you should do:

1.　　   Keep calm. Save your strength and breath.

2.　　   Try to float on your back or tread(踩)water. To tread water, move your feet as if you are climbing some stairs.

3.　　   Raise your right arm for help.

Remember: A red flag means that it is dangerous for all swimmers to enter the water. A blue flag means that it is dangerous for children and weak swimmers to enter the water.

1．When you see a red flag, you know that　　   .

A. no one should swim there

B. anyone may swim there

C. only strong swimmers should swim there

D. children should swim there

2．We can go swimming   　　.

A. after a meal　　　　　　　　　　　　  B. if we have a ring

C. in deep cold water　　　　　　　　　　 D. with our friends

3．We should dive only when　　    .

A. the water is deep enough

B. the water is warm

C. the water is cold

D. we are not alone

4．What the writer wants to say is 　　　　.

A. rings and floats are of no use

B. boats are not safe

C. we must be very careful in swimming

D. swimming is a bad sport

5．We should　　   when in difficulty.

A. hold our breath

B. keep calm and let other know

C. put up our arms

D. be silent