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[主观题]

There are some earth phenomena you can count on, but the magnetic field, some say, is not

one of them. It fluctuates in strength, drifts from its axis, and every few 100,000 years undergoes a dramatic polarity reversal—a period when north pole becomes south pole and south pole becomes north pole. But how is the field generated, and why is it so unstable？

Groundbreaking research by two French geophysicists promises to shed some light on the mystery. Using 80 meters of deep sea sediment (沉淀物) core, they have obtained measurements of magnetic-field intensity that span 11 polarity reversals and four million years. The analysis reveals that intensity appears to fluctuate with a clear, well-defined rhythm. Although the strength of the magnetic field varies irregularly during the short term, there seems to be an inevitable long-term decline preceding each polarity reversal. When the poles flip—a process that takes several hundred thousand years—the magnetic field rapidly regains its strength and the cycle is repeated.

The results have caused a stir among geophysicists. The magnetic field is thought to originate from molten (熔化的) iron in the outer core, 3,000 kilometers beneath the earth's surface. By studying mineral grains found in material ranging from rocks to clay articles, previous researchers have already been able to identify reversals dating back 170 million years, including the most recent switch 730, 000 years ago. How and why they occur, however, has been widely debated. Several theories link polarity flips to external disasters such as meteor (陨星) impacts. But Peter Olson, a geophysicist at the Johns Hopkins University in Baltimore, says this is un. likely if the French researchers are right. In fact, Olson says intensity that predictably declines from one reversal to the next contradicts 90 percent of the models currently under study. If the results prove to be valid, geophysicists will have a new theory to guide them in their quest to understand the earth's inner physics. It certainly points the direction for future research.

Which of the following titles is most appropriate to the passage？

A．Polarity Reversal: A Fantastic Phenomenon of Nature.

B．Measurement of the Earth's Magnetic-Field Intensity.

C．Formation of the Two Poles of the Earth.

D．A New Approach to the Study or Geophysics.

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发布时间：2020-12-14
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更多“There are some earth phenomena you can count on, but the magnetic field, some say, is not”相关的问题

第1题

What have the two French geophysicists discovered in their research？A) Some regular

What have the two French geophysicists discovered in their research？

A) Some regularity in the changes of the earth’s magnetic field.

B) Some causes of the fluctuation of the earth’s magnetic field.

C) The origin of the earth’s magnetic field.

D) The frequency of polarity reversals.

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第2题

There is hardly an environment on earth ________ some species of animal or other ha
s not adapted successfully.

A) to which

B) wherever

C) so that

D) as to

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第3题

Different from animals, the trees influence the earth's atmosphere by ______.A．expelling c

Different from animals, the trees influence the earth's atmosphere by ______.

A．expelling carbon dioxide from their leaves

B．expelling oxygen from their leaves

C．directly reduce the blanket of gases

D．turning some carbon dioxide into lignin

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第4题

What will happen if the gravity suddenly disappeared？
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A. Nothing on Earth will begin to float.

B. The air will leap into space in a minute.

C. Some of the living things will die gradually.

D. Water is everywhere on Earth.

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第5题

What does the author imply by saying "living space...is figured...also in cubic volume abo
ve the earth" in Para. 3？

A．We need to take some measures to protect space.

B．We must preserve good living conditions for both birds and land animals.

C．Our living space should be measured in cubic volume.

D．Our living space on the earth is getting smaller and smaller.

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第6题

听力原文：Some parts of the earth are more likely to have quakes than others. This is usual

听力原文： Some parts of the earth are more likely to have quakes than others. This is usually true of mountain areas, because there the thickness of rocks, which make up the earth's crust, is not even. But quakes may often be felt in level regions, too, because the waves, which come from the center of a quake, run often for thousands of miles.

It is easy to understand why man is so frightened by an earthquake. People used to think that when there was an earthquake, the ground opened, swallowed great numbers of people, then closed, and those who were killed disappeared forever. We know now this does not happen.

What we need to fear are the after-effects of a serious earthquake: fires, floods, and landslides. Since the Yellowstone earthquake some people have said that they would never go to that area for fear of being caught in a landslide occurring after the earthquake. This is, actually a foolish idea. Such a fear would keep us away from mountains the rest of our lives. Even though earthquakes happen every day something like the Madison River landslide does not happen very often. We can realize gratefully that few of us will suffer because of such a disaster. At the same time we can understand the need of being ready to help those who do suffer such trouble.

(33)

A．Because the waves coming from the center of a quake can spread to these places.

B．Because there are the thickness of rocks making up the earth's crust.

C．Because some parts of the earth are more likely to have quakes than others.

D．Because mountainous areas are easy to have earthquakes.

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第7题

What does the author imply by saying “living space... is figured... also in cubic v
olume above the earth” (Lines 7-8, Para. 3)？

A) Our living space on the earth is getting smaller and smaller.

B) Our living space should be measured in cubic volume.

C) We need to take some measure to protect space.

D) We must preserve good living conditions for both birds and animals.

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第8题

What do you think about the future of earth？ Are you pessimistic, or optimistic？ Give your
opinions on A Hundred Years from Now in a passage of about 120 words.

1. Some people are pessimistic when they think about the future.

2. Other people believe that man adapts very easily.

3. If we are to have a bright future, we have to take measures now.

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第9题

听力原文：Experts say some farming activities are seriously damaging Earth's environment. B

听力原文： Experts say some farming activities are seriously damaging Earth's environment. Bad farming methods can damage soil, forests and water supplies. They also have caused some plants and animals to disappear.

Two groups now say that bad farming methods are threatening the ability of farmers to produce enough food to feed the world population in the future.

The groups used satellite images, maps and modern equipment to study the effect of agriculture on the environment. The study found that the destruction of soil is widespread. Important organic nutrients are being removed from farmland.

Agriculture uses seventy percent of the freshwater in the world each year. The study found that many farmers are wasting water supplies. In addition, chemicals designed to protect crops may pollute waterways.

The report also says as much as thirty percent of the world's forests have been cut down so the land could be used for agriculture. This has led to a severe loss of wildlife and their environments.

(30)

A．Soil.

B．Human population.

C．Forest.

D．Water.

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第10题

While flying in space, astronauts have no weight. It is a condition of weightlessness.
How does this affect their heart and blood vessels？ What happens to their hearts and blood vessels when they go into space？

On earth gravity (引力) makes blood flow down towards the feet, so the heart must work to pump blood up. In space blood flows up towards the heart. The effect is similar to what happens when you lie with your feet up and your head down. The flowing blood is felt by receptors in the walls of arteries (动脉) in the upper part of the body and in the heart. These receptors send signals to the brain, but the brain reads them incorrectly. To the brain, the signals means the amount of blood in the body has increased, so the brain tells other parts of the body to react to the increase in the blood. For example, the body produces more urine (尿液), resulting in loss of body fluid and salt. At the same time the astronaut has less desire to drink and so does not replace the lost fluid.

As a spacecraft begins to fall back to earth atmosphere, the crew begins to feel gravity. Blood again flows towards the feet and collects there. The heart beats faster in an effort to pump enough blood to the brain. Some crew members may not get enough blood to the brain and the heart beats too fast. They become sick and even lose consciousness as their spacecraft reenters the earth atmosphere. To prevent this, special clothing is invited for astronauts to prevent blood collecting in their legs. They put it on just before the craft reenters the earth’s atmosphere. They also drink about a liter (升) of water and eat some salt to replace the fluid they have lost while in space.

Weightlessness affects the heart and blood vessels in another way. The heart does not work as hard in a weightless environment as it does in an environment of gravity. When the heart works less hard, the heart muscles become weaker. It is replaced by fibrous tissue and fat

41.If one lies with his feet up and his head down on earth, his()

A.blood will flow up towards the heart.

B.blood will flow down towards the feet.

C.heart will pump the blood up to the head.

D.heart will have to work harder.

42.What can we infer from the second paragraph of the passage()

A.The brain reads the signals incorrectly because it tends to go wrong in outer space

B.In space an astronaut should drink some water even when he does not feel thirsty.

C.In space the amount of water in the body of an astronaut increase.

D.The receptors in the walls of arteries often send wrong signals to the brain.

43.When the spacecraft reenters the earth’s atmosphere some astronauts become sick or even lose consciousness because()

A.their brains cannot get enough blood

B.their hearts are not strong enough

C.their blood collects in their feet

D.they begin to feel the gravity again

44.When the spacecraft enter the earth’s atmosphere, the astronauts should do the following except()

A.trying to regain their consciousness

B.eating some salt

C.drinking some water.

D.putting on special clothing

45.After a long time in space, an astronaut’s heart muscles become weaker because()

A.they are short of exercises when the heart works less hard.

B.the heart works too hard under an environment of weightlessness.

C.the astronaut’s hard work puts too great a burden on the heart.

D.they are completely replaced by fibrous tissue and fat.

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第11题

Which statement about Newton and Einstein is NOT true？A．They both committed to the study o

Which statement about Newton and Einstein is NOT true？

A．They both committed to the study of space and time and put forward their own theories.

B．Einstein's theory of relativity preceded the theories about the black holes.

C．Newton believed that the laws of motion are different for objects on Earth and in space.

D．Einstein's theory of relativity proved that some of the Newton's beliefs were wrong.

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