in the air, this kind of steel become harder and harder. A. Cooling B.Having cooled C.Being cooled D.Cooled 题目和参考答案——青夏教育精英家教网—

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___in the air, this kind of steel become harder and harder.

A. Cooling B.Having cooled C.Being cooled D.Cooled

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　　The idea of fighting a noise by making more noise sounds strange, but What's exactly that motor engineers are doing in Germany and some other countries．

　　Carmakers' research and development laboratories have already proved that mixing in more noise with the help of loudspeakers can reduce the unwanted noise．

　　Physicists have known about the technique for a long time．Sound is make up of pressure waves in the air．If two sound waves of the same frequency(频率)mix so that the highest point of one wave happens at the same time with the lowest point of the other wave, the result is no sound．Therefore, by producing a perfect copy of the noise and delaying it by half a wave cycle(周期), we can kill the unwanted noise．Using this technique many carmakers are racing to develop noise-killing systems both inside and outside the cars．Another good thing about the use of noise-killing systems is that it saves the need for a silencer, which not only reduces the weight of a car, but also makes the motor bum less oil and work better．

　　Some engineers believe that the noise-killing system will be used in most cars in 1996．But the carmakers haven't decided if they will put it into production because it would add several hundred dollars to the cost of their ears．

(1)

Which of the following gives a general idea of how the noise-killing system works?
[　　]
A．	By producing pressure waves going in the opposite direction．
B．	By mixing high frequency sound waves with low frequency sound waves．
C．	By making copies of the unwanted sound waves and letting them out a little later．
D．	By mixing new sound waves with the noise and sending them out together．

(2)

Besides its main function the noise-killing system can ________．
[　　]
A．	make a car lighter
B．	make a car quieter
C．	reduce the cost of a silencer
D．	improve the performance of a silencer

(3)

The noise-killing system is not yet popular mainly because ________．
[　　]
A．	it increases the cost of car production
B．	carmakers are not sure if it is necessary
C．	it is still being tried out
D．	people still have their doubts

We've used the wind as an energy source for a long time. The Babylonians and Chinese were using wind power to pump water for irrigating crops 4,000 years ago, and sailing boats were around long before that. Wind power was used in the Middle Ages, in Europe, to grind(磨碎) corn, which is where the term "windmill" comes from.

We can use the energy in the wind by building a tall tower, with a large propellor on the top. The wind blows the propellor round, which turns a generator to produce electricity. We tend to build many of these towers together, to make a "wind farm" and produce more electricity. The more towers, the more wind, and the larger the propellors, the more electricity we can make. It's only worth building wind farms in places that have strong, steady winds, although boats and caravans（大篷车）increasingly have small wind generators to help keep their batteries charged.

The best places for wind farms are in coastal areas, at the tops of rounded hills, open plains and gaps in mountains—places where the wind is strong and reliable. Some are offshore. To be worthwhile, you need an average wind speed of around 25 km/h. Most wind farms in the UK are in Cornwall or Wales. Isolated places such as farms may have their own wind generators. In California, several “wind farms” supply electricity to homes around Los Angeles.

The propellors are large, to obtain energy from the largest possible volume of air. The blades can be angled to cope with varying wind speeds. Some designs use vertical turbines(垂直涡轮机), which don't need to be turned to face the wind. The towers are tall, to get the propellors as high as possible, up to where the wind is stronger. This means that the land beneath can still be used for farming.

1. The first paragraph aims to introduce to us _______.

A. the function of wind power B. the source of wind power

C. the nations using wind power D. the history of using wind power

2.How does a wind power work?

A. The generator turns the propellor blades and produce electricity.

B. The tall tower helps turn the energy in the air into electricity.

C. Warm air rises and makes the propellor move round.

D. The propellor blown round by wind turns the generator to produce electricity.

3. The best places for building the wind farm are places where _______.

A. boats and caravans can often be seen B. isolated farms don’t have enough electricity

C. there are less human activities D. the wind is strong and reliable

4. We can infer from the passage that _______.

A. wind farms will not take up too much farming land

B. wind farms need no fuel because wind is free

C. the blades can be angled to turn to face the wind wherever it comes from

D. the higher and larger the towers are, the stronger the wind is

5. What can be a suitable title for the passage?

A. Where to build a wind farm. B. ABC of the using of wind energy.

C. How to make best use of wind. D. Wind energy is the best energy.

It was once thought that air pollution affected only the area immediately around large cities with factories and/or heavy automobile traffic. Today, we know that although these are the areas with the worst air pollution, the problem is literally worldwide. On several occasions over the past decade, a heavy cloud of air pollution has covered the entire eastern half of the United States and led to health warnings even in rural areas away from any major concentration of manufacturing and automobile traffic. In fact, the very climate of the entire earth may be affected by air pollution. Some scientists feel that the increasing concentration of carbon dioxide in the air resulting from the burning of fossil fuels(coal and oil) creating a greenhouse effect-holding in heat reflected from the earth and raising the world’s average temperature. If this view is correct and the world’s temperature is raised only a few degrees, much of the polar ice cap will melt and cities such as New York, Boston, Miami, and New Orleans will be under water.

Another view, less widely held, is that increasing particulate matter in the atmosphere is blocking sunlight and lowering the earth’s temperature-a result that would be equally disastrous（灾难的）. A drop of just a few degrees could create something close to a new ice age, and would make agriculture difficult or impossible in many of our top farming areas. At present we do riot know for sure that either of these conditions will happen(though one recent government report prepared by experts in the field concluded that the greenhouse effect is very likely). Perhaps, if we very lucky, the two tendencies will offset each other and the world’s temperature will stay about the same as it is now.

1.As pointed out at the beginning of the passage, people used to think that air pollution ______.

A．caused widespread damage in the countryside

B．affected the entire eastern half of the United States

C．almost brought worldwide effect

D．existed merely in urban and industrial areas

2.As far as the greenhouse effect is concerned, the author _____________.

A．shares the same view with the scientists

B．is uncertain of its occurrence

C．rejects it as being ungrounded（无根据的）

D．thinks that it will increasingly destroy the world soon

3.It can be inferred from the passage that .

A．raising the world’s temperature a little would not do much harm to life on the earth

B．lowering the world’s temperature a little would lead to agricultural disasters

C．almost no temperature variations have occurred over the past decade

D．the world’s temperature will remain stable forever

4.This passage is primarily concerned with .

A．the greenhouse effect in the world

B．the measures to adjust the climate

C．the potential effect of air pollution

D．the measures to protect the environment

A kind of little cars may some day take the place of today’s ones. If everyone drives such cars in the future, there will be less pollution in the air. There will also be more space for parking cars in cities, and the streets will be less crowded. Three such cars can fit in the space now needed for one car of the usual size.

The little cars will cost much less to own and to drive. Driving will be safer, too, as these little cars can go only 65 kilometers an hour.

The cars of the future will be fine for getting around the city, but they will not be useful for long trips. Little cars will go 450 kilometers before needing to stop for more gasoline.

If big cars are still used along with the small ones, two sets of roads will be needed in the future. Some roads will be used for the gig, fast cars and other roads will be needed for the slower small ones.

1.There is much pollution in the air today because ___________.

A. people drive big cars

B. people drive little cars

C. the cars go 65 kilometers an hour

D. the cars can go 450 kilometers an hour

2.The usual size of cars today is _______ that of the future cars.

A. much smaller than B . much the same as

C. three times as large as D. a little larger than

3. Which of the following is NOT true?

A. Big cars cost more to own and to drive

B. Big cars are not useful for long trips

C. The cars of the future will be smaller than today’s cars.

D. Small cars are slower than big cars.

4.The street will be less crowded because ______________.

A there will be fewer cars in the future

B. driving future cars will be safer

C. there will be fewer passengers in the street

D. future cars will be much smaller

5. Two sets of roads may be needed in the future because_________.

A. there will be too many cars in the future

B. more and more people will get around a city

C. bit cars and little cars may be used along with each other

D. it looks more beautiful to have two sets of roads

Napoleon Bonaparte died on May 5, 1821, on the island of St. Helena off the coast of Africa. He was 51 years old at the time. When doctors examined Napoleon’s body, they said that the former emperor of France had died from cancer of the stomach. That was the cause of death recorded in the official report. However, other doctors disagreed. One doctor who was present during the examination of the body said that Napoleon died of hepatitis. Other historians and medical experts have suggested that Napoleon died of syphilis, tuberculosis, or perhaps malaria. Now, after careful research, a British chemist thinks that Napoleon might have been poisoned -- not by a person, but by his wallpaper.

Napoleon was sent to the island of St. Helena in 1815 after he lost the battle of Waterloo. He was a prisoner on the island. Although he had servants to attend to him, he had to live in one small building. St. Helena is a very wet island, so the walls of the building were always covered with mold. Napoleon became ill from spending too much time inside his house. Almost constantly he had a fever, chills, and felt sick to his stomach. He often felt pain in his shoulders and in his side. His skin turned yellow. He got frequent headaches, and he would become dizzy and vomit(吐). None of the medicine that the doctors gave Napoleon seemed to help. They were not sure what was the matter. Finally, Napoleon was too weak to leave the house. One night, while he was sleeping, he went into a coma and died.

Many doctors who later reviewed the reports of Napoleon’s illness found that the symptoms(症状) did not show a man who suffered from stomach cancer. It seemed obvious that Napoleon had died from some other cause. In 1961, a Swedish doctor examined some of Napoleon’s hair and found a high level of arsenic, a chemical poison. Was Napoleon murdered? It is doubtful. Arsenic was used in many types of medicine during Napoleon’s time, so he might have taken the arsenic as a cure for his illness. Then, in 1982, Dr. David Jones from England began to look into the mystery and suggested that Napoleon might have breathed in arsenic which was in the air of his house. In the 1700s and 1800s, arsenic was used to make a kind of green paint used on cloth and wallpaper. If the paint was used on a wet wall, the arsenic would go into the air. A person in the room might breathe that air. After studying the wallpaper in the room where Napoleon died, Dr. Jones found high levels of arsenic in the green paint on the walls.

1.Why did Napoleon live on St. Helena?

A．He owned the island.	B．He was a prisoner there.
C．His family lived there.	D．He liked the island.

2.The official report said that Napoleon died of____________.

A．cancer

B．a coma

C． mold

D．poison

3.Napoleon suffered from the following symptoms except __________.

A. chills B. fever C dizziness D. bleeding

4.According to Dr. Jones, how did the arsenic probably get into Napoleon’s body?

A．He drank it..

B．He touched it.

C．He breathed it in.

D．He ate it

5.The passage says that .

A．a British doctor thinks he has found the cause of Napoleon’s death

B．many doctors have tried to guess the cause of Napoleon's death

C．Napoleon could have died from poison

D．all of the above

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