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　　It is well known that smoking causes harmful side effects; however, we see thousands of smoking. Not only the elderly;  1 young people and children are under smoke, in order to show they  2 ——maybe smoking is a  3 of being a grown up.  4 smoking has become a serious social problem.

　　Our government has  5 called on people to  6 smoking. As a result, many have given up smoking.  7 , a lot more people are joining the ranks of smokers.  8 it is far from enough to  9 the matter to slogans(口号).  10 is necessary is a campaign  11 smoking.

　　First, I suggest, regulations  12 be made to forbid smoking in public places. In many cities smoking is not  13 in cinemas or in theatres. Smokers have to abide by(遵守)it,  14 they'll be fined. Why can't we  15 this as a good example to develop it in other public places  16 on the trains, in the offices, hotels and so on?

　　Secondly, stricter measures  17 taken to impose a tax  18 smokers for causing pollution.  19 we'll continue the fight against smoking in the  20 that one day smokers will fully realize the health dangers they face.

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　　For years scientists have been worried about the effects of air pollution on the earth’s natural conditions. Some believe the air inside many houses may be more dangerous than the air outside. It may be one hundred times worse.

　　Indoor air pollution can cause a person to feel tired, to suffer eye-pain, headache and other problems. Some pollutants（ 污染 物） can cause breathing disorders, diseases of blood and even cancer, Most scientists agree that every modern house has some kind of indoor pollution. People began to notice the problem in the early 1970s. It is that when builders began making houses and offices they did not waste energy. To do this they built buildings that limited the flow of air between inside and outside. They also began using manmade building materials. These materials are now known to let out harmful gases. As the problem became more serious, scientists began searching for a way to deal with it. They discovered a natural pollution control system for building— green plants. Scientists do not really know how plants control air pollution. They believe that a plant’s leaves absorb or take in the pollutants. In exchange the plant lets out oxygen through its leaves and through its tiny organizations on its roots. Scientists suggest that all buildings should have one large plant or several small plants inside for every nine square metres of space. Studies of different plants show that each absorbs different chemicals. So the most effective way to clean the air is to use different kinds of plants. Having green plants inside your house can make it a prettier and more healthy place.

　　Generally speaking, indoor air pollution may be more harmful than the air outside because ________.

　　A. the man - made building materials let out dangerous gases inside houses

　　B. there may be more harmful gases outside houses

　　C. the flow of air indoors is limited

　　D. indoor air pollution can make a person seriously ill

　　The most effective way to clean the air is to use different kinds of plants because________.

　　A. they may let out more oxygen which people need

　　B. they can absorb different kinds of the harmful indoor chemicals

　　C. they can take in all kinds of indoor pollutants

        D. they can make your house prettier and more healthy

London has always been known for its "black fogs. “ In the winter of 1952，a milky white fog rolled into the city. As the smoke poured into the air, it was so hard to see that people had to walk in front of the buses to guide them. In this way, the most serious air pollution disaster in history began. When it was over, more than 4,000 people had been killed by the thick black smog.

New York City has had several London-type smogs since 1950. Each time, there were from 100 to 400 deaths caused by the smog. Although these smogs were not as deadly as London’ s,

New York City has the worst air pollution problem in the United States.

In all the killer smogs, factories and homes poured smoke and fumes into the air from the furnaces. The chemical fumes combined with the water droplets in the fog to form harmful substances. These substances caused the illness of those who breathed the polluted air.

Usually, such harmful fumes rise into the upper air and are blown away by the wind. But sometimes there is an unusual weather condition called a temperature inversion. A layer of cold air remains near the ground as smoke and fumes pour into it. This is covered by an upper layer of warm air that acts like a lid. It prevents the polluted cooler air from rising. The harmful fumes pile up and make people ill. The smog may be so thick that airports are closed and chains of collisions occur on the highways.

Another type of smog occurs in Los Angeles. Here the weather may be clear and sunny. But stinging eyes and dry coughs show that harmful chemicals fill the air. The smog is due to invisible gases, mostly from automobile exhaust. Because these chemicals are changed by the sun high up in the air, it is called photochemical smog. It contains automobile exhaust fumes and nitrogen oxides changed by the sun's rays. Added to these are sulfur dioxide and other ^{fumes from} factories and oil refineries. Photochemical smog is found in many large cities all over the world.

Killer smogs don，t happen very often, fortunately. But in Beijing, a combination of automobile exhaust fumes, home furnace smoke, and factory waste gases pours into the air. This may also happen in the suburbs, or out in the country, where large factories have been built. A number of harmful substances have been found in the air there. When these substances are breathed in day after day ，the health of the population is affected.

51.    Why do people call this phenomenon " black fog" ？

A. It is black and dirty.                        B. It can affect the health.

C. It can kill people.                            D. It is too thick for people to see something.

52.    What can reduce the air pollution according to the passage?

A. Water.                    B. Wind.                  C. The sun.                  D. Cold air.

53.When photochemical smog happens in the city, _____.

A. many people will be killed                B. black smoke may pour into the air

C. the weather may be fine                   D. people have to walk to work

54.From the passage we know that the most serious black smog disaster took place in_____

A, London               B. New York             C. Los Angeles              D. Beijing

For years scientists have been worried about the effects of air pollution on the earth’s natural conditions. Some believe the air inside many houses may be more dangerous than the air outside. It may be one hundred times worse.

      Indoor air pollution can cause a person to feel tired, to suffer eye pain, headache and other problems. Some pollutants (污染物) can cause breathing disorders, diseases of blood and even cancer. Most scientists agree that every modern house has some kind of indoor pollution.

      People have paid more attention to the problem now. It is said that when builders began making houses and offices they did not waste energy. To do this they built buildings that limited the flow of air between inside and outside. They also began using man-made building materials. These materials are now known to let out harmful gases.

      As the problem became more serious, scientists began searching for a way to deal with it. They discovered a natural pollution control system for building--- green plants. Scientists do not really know how plants control air pollution. They believe that a plant’s leaves absorb or take in the pollutants. In exchange the plant lets out oxygen through its leaves and small organizations on its roots. Scientists suggest that all buildings should have one large plant or several small plants inside for every nine square metres of space. Studies of different plants show that each absorbs different chemicals. So the most effective way to clean the air is to use different kinds of plants. Having green plants inside your house can make it a prettier and more healthy place.

Some kind of indoor pollution can be found in ________.

     A. every modern house     B. every old house       

  C. all kinds of houses        D. all kinds of offices

The indoor air pollution is caused by ________.

A. the limit of the flow of air between inside and outside

B. the building way that the builders want to save energy

C. the building things that are made of man-made materials

D. the man-made building materials and the limit of air-flow

The reason why we should use different kinds of plants to clean the air is that ________.

A. plants can let out all kinds of pollutants indoors

B. plants may take in more oxygen which people need

C. plants can absorb all kinds of harmful indoor chemicals

D. plants can make our houses prettier