听力原文:Scientists have observed that plants themselves produce many poisonous chemicals - 试题答案网问答

第1题

听力原文：The earthquake that shook Los Angeles in 1994 claimed the death of more than 60 p

eople. According to scientists, the damage and death toll could have been much worse if it wouldn't occur in the early morning of a holiday.

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第2题

听力原文：It was not until one hundred and fifty years ago that scientists learned about th

听力原文： It was not until one hundred and fifty years ago that scientists learned about the existence of dinosaurs. Thanks to an English doctor and his wife, the door was opened to this zoological study. Reasoning that these animals' tremendous size must have made them terrible creatures, scientists combined two Greek words, deimos, meaning terrible, and sauros, meaning lizards, to form. the word dinosaur.

After many years of study, they determined that these beasts roamed the earth for millions of years, and ceased to exist some sixty million years ago.

Unbelievable as it may seem, not all dinosaurs were carnivorous, that is, meat eating. Many were herbivorous, or vegetarians.

By reassembling the bones found at digging sites, scientists have been able to reconstruct the skeletons and learn great deal about the dinosaur's living conditions. They have learned that dinosaurs inhabited not only the land, but also the water and sky.

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A．Beasts.

B．Herbivorous.

C．Carnivorous.

D．Dinosaurs.

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第3题

听力原文：Scientists have discovered that plants themselves produce many poisonous chemical

听力原文： Scientists have discovered that plants themselves produce many poisonous chemicals for defense against insects. But insects have developed ways of dealing with them and, in fact, have been eating plants for about 250 million years. Now insects are using these same mechanisms to deal with man-made poisons—insecticides. This is why resistance of insects to insecticides has developed so rapidly.

What should be done？ Scientists studying the problem suggest that farmers use less insecticides. At the moment, farmers regularly spray crops as a precaution against problems that are caused by large numbers of pests. They should, instead, spray only where pests have actually been seen. Secondly, farmers could use a combination of two or three insecticides at once. To survive, the insects would need to become resistant to two or more insecticides at the same time.

The most surprising suggestion, perhaps, is that at certain times of the year, farmers should actually try to attract insects onto the crops they are trying to protect. The new insects will mate with those which survived from a certain kind of insecticide and will lessen the latter's resistance to it.

Scientist hope that these and other measures will postpone the day when farmers and scientists will have to stand by while new super-bugs which may be resistant to all poisons invade our farms and devour our crops.

What have scientists discovered about plants and insects？

A．Plants produce many poisonous chemicals for defense against insects.

B．Insects develop ways of dealing with natural poisonous chemicals but not man-made ones.

C．Farmers must spray plants all the time.

D．Farmers must use different brands of insecticides.

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第4题

听力原文：Why don't birds got lost on their long migratory flights？ Scientists have puzzled

听力原文： Why don't birds got lost on their long migratory flights？ Scientists have puzzled over this question for many years. Now they're beginning to fill in the blanks.

Not long ago, experiments showed that birds rely on the sun to guide them during daylight hours. But what about birds that fly mainly by night？ Tests with artificial stars have proved conclusively that certain night-flying birds are able to follow the stars in their long-distance flights.

One such bird—a warbler—had spent its lifetime in a cage and had never flown under a natural sky. Yet it showed an inborn ability to use the stars for guidance. The bird's cage was placed under an artificial star-filled sky at migration time. The bird tried to fly in the same direction as that taken by his outdoor cousins. Any change in the position of the make-believe stars caused a change in the direction of his flight.

Scientists think that warblers, when flying in daylight, use the sun for guidance. But the stars are apparently their principal means of navigation. What do they do when the stars are hidden by clouds？ Apparently, they find their way by such landmarks as mountain ranges, coast lines, and rivet courses. But when it's too dark to see these, the warblers circle helplessly, unable to get their bearings.

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A．Birds have to be taught to navigate.

B．A bird that has been caged will not.

C．Some birds cannot fly at night.

D．Some birds seem instinctively to follow the stars when flying at night.

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第5题

听力原文：A few months ago, [32]a team of interviewers were sent to schools to find out why

听力原文： A few months ago, [32]a team of interviewers were sent to schools to find out why children are prejudiced against science. Their answer provided this surprising picture of a typical scientist: they thought [33]a scientist is a rather dull person who spends all day working in a laboratory, wearing a white coat and making things that smell bad. They thought that scientists usually aren't very interesting and don't talk about anything but science. They don't play games well and they aren't attractive to the opposite sex. They also did not realize that women are as capable of becoming scientists as men.

On the other hand, [34]an art graduate is seen as a much livelier person. Arts graduates are thought to have a better sense of humor, to be interested in sports and pop music and to be considered attractive. When you understand these misconceptions which children have, it is only logical that most of them want to study arts rather than science.

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A．Scientists.

B．Art graduates.

C．Children.

D．Women.

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第6题

听力原文：A few months ago, [32] a team of interviewers were sent to schools to find out wh

听力原文： A few months ago, [32] a team of interviewers were sent to schools to find out why children are prejudiced against science. Their answer provided this surprising picture of a typical scientist: they thought [33] a scientist is a rather dull person who spends all day working in a laboratory, wearing a white coat and making things that smell bad. They thought that scientists usually aren't very interesting and don't talk about anything but science. They don't play games well and they aren't attractive to the opposite sex. They also did not realize that women are as capable of becoming scientists as men.

On the other hand, [34] an art graduate is seen as a much livelier person. Arts graduates are thought to have a better sense of humor, to be interested in sports and pop music and to be considered attractive. When you understand these misconceptions which children have, it is only logical that most of them want to study arts rather than science.

(33)

A．Scientists.

B．Art graduates.

C．Children.

D．Women.

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第7题

听力原文：The year is 2501, and the Earth is desperately short of fuel. All Earth's coal, o

听力原文： The year is 2501, and the Earth is desperately short of fuel. All Earth's coal, oil and wood have been used up long ago, and scientists have been sent to the ends of the universe in search of alternative forms of energy.

A rich and powerful civilization has been discovered on the planet Jupiter, and Earth is supplied with fuel by constant supply fleets from that planet, but the price is very high. Unless it discovers an alternative source of energy soon, civilization on Earth will fail, and its inhabitants will have to move to other planets where they will be little more than slaves. Then Jupiter will take possession of Earth-- the most beautiful, most desirable planet in the universe.

Human scientists have been sure for a long time that Jupiter possesses a method of creating constant energy and now ten explorers on a secret mission from Earth have discovered the secret--a kind of heavy, green dust which will change salt water to high grade petroleum. This dust covers a large part of Jupiter's surface, and just a few pounds of it could solve the world's energy crisis since it would reproduce itself continuously in Earth's atmosphere.

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A．Explorers.

B．Doctors.

C．Teachers.

D．Coal-miners.

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第8题

听力原文：Man has a big brain. He can think and speak. Scientists used to think that men ar

听力原文： Man has a big brain. He can think and speak. Scientists used to think that men are different from animals because they can think and learn. They now know that animals can learn —dogs, rats, birds —and worms —can learn. So scientists are beginning to understand that men are different from animals because they can speak. Animals cannot speak. They make noises when they are afraid, or angry, or unhappy. Apes are our nearest cousins. They can understand some things more quickly than human beings, and one or two have learned a few words. But they are still different from us. They cannot join words and make sentences. They cannot think like us because they have no language. They can never think about the past or the future.Language is a wonderful thing. Man has been able to develop civilization because he has language. Every child can speak his own language very well when he is four or five —but no animal learns to speak. How do children learn？ Scientists do not really know. What happens when we speak？ Scientists do not know. They only know that man can speak because he has a big brain.

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A．Because he has a big brain.

B．Because he learns to speak.

C．Because he develops civilization.

D．Because he knows many words.

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第9题

听力原文：Not long ago, some of you may have read about the team of mountain climbing scien

听力原文： Not long ago, some of you may have read about the team of mountain climbing scientists who helped to recalculate the elevation of the highest mountain in the world, Mount Everest. Of course the elevation of Mount Everest was determined many years ago using traditional surveying methods. But these scientists wanted to make a more precise measurement, using a new method that takes advantage of recent advances in technology; it's called the Glob al Positioning System. The Global Positioning System uses 24 satellites that circle the earth. Each of the satellites is constantly sending out signals, and each signal contains important information that can be used to determine the longitude, latitude and elevation at any point on the earth’s surface. Well in order to use the system to calculate a mount of Everest's elevation, scientists need to put a special receiver on the summit to receive signals from the satellites. The problem with this was that in the past, the receivers were much too heavy for climbers to carry. But now these receivers have been reduced to about the size and weight of a hand-held telephone, so climbers were able to take the receiver to the top of the Everest, and from there, to access the satellite system signals that would allow them to determine the precise elevation. And it turns out that the famous peak is actually a few feet higher than us previously thought.

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A．The advantages of traditional surveying methods.

B．Using satellites to communicate with mountain climbers.

C．Obtaining new information about a mountain.

D．Controlling satellites from the top of a mountain.

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第10题

听力原文：Not only farmers but also scientists have studied weather forecasting. People for

听力原文： Not only farmers but also scientists have studied weather forecasting. People for many centuries and in all countries have studied the weather and tried to make weather forecast. Sometimes distant objects such as hills and tall trees seem to be very clear and near. This is a sign of much water in the air, and therefore rain will probably come. When distant sounds, such as noise from a train, birds singing, people shouting, are very clearly heard, then wet and stormy weather is on the way. (30)Some birds, particularly swallows, fly high if fine weather is coming, but they fly very near the ground if rainy weather or a storm is on the way. This is because probably the insects, which they are hunting, then fly low. (31)If you see a rainbow during rainy weather, this is a sign that the weather will clear up and become fine. Such rainbows always come in the evening. If the stars twinkle-clearly at night, then fair weather will continue. If a mist appears in the early morning, just about sunrise, then the day will be warm. If the sunset is mostly red in color, then the following day will be fine. When big clouds disappear at sunset, then the weather will follow on the next day. (32)If a rainbow appears in the morning, then rainy weather will probably come. Most of the above sayings have been made up by people who have used their eyes and their brains to forecast the weather.

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A．Because both farmers and scientists try to make weather forecast.

B．Because people in all countries make weather forecast.

C．Because it is easy to make weather forecast.

D．Because he wants to make it clear how important to make weather forecast.

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听力原文：Scientists have observed that plants themselves produce many poisonous chemicals