相关试题
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第二篇
Are These Food Safe to Eat?
Traditionally,in plant breeding,there are crossing varieties of the same species in ways they could cross naturally.For example,disease-resistant varieties of wheat have been crossed with highyield wheat to combine these properties.This type of natural gene exchange is safe and fairly predictable.
Genetic engineering(GE)makes it possible to exchange genes between unrelated species that cannot exchange genes with each other in a natural way.GE can involve the exchange of genes be-tween vastly different species一e.g. putting scorpion toxin genes into maize or fish antifreeze genes into tomatoes.It is possible that a scorpion toxin gene,even when it is in maize DNA,will still get the organism to produce scorpion toxin一but what other effects may it have in this alien environment? We have already realized this problem一adding human growth hormone genes to pigs certainly makes them grow一but it also gives them arthritis and makes them cross-eyed,which was entirely out of expectation.
It won't be difficult to find out,for example,that the gene for human intelligence will not have the same effect if it is inserted into cabbage DNA as it had in human DNA一but what side-effect would it have?In other words,is genetically modified(GM)food safe to eat?The answer is that no-body knows because long-term tests have not been carried out.
Those companies who want a GM product approved in the UK or USA are required to provide regulatory bodies with results of their own safety tests.Monsanto's soya beans were apparently fed to fish for 10 weeks before being approved.There was no requirement for independent testing,for longterm testing,for testing on humans or testing for specific dangers to children or allergic people.
The present opinion of the British Government is that"There is no evidence of long-term dangers from GM foods."In the US,the American Food and Drug Administration is now being prosecuted for covering up research that suggested possible risks from GM foods.
Which statement about GM product is true according to the passage?
A:Adding human growth hormone genes to pigs does not make them grow.
B:The American Food and Drug Administration is now doing a research that suggested possible risks from GM foods.
C:The gene for human intelligence will not have the same effect if it is inserted into cabbage DNA as it had in human DNA.
D: There has been requirement for independent testing,for long-term testing,for testing on humans or testing for specific dangers to children or allergic people.
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第一篇
Can Buildings Be Designed to Resist Terrorist Attack?
In the aftermath of the terrorist attack on the World Trade Center,structural engineers are trying hard to
solve a question that a month ago would have been completely unthinkable:Can buildings be designed to
withstand catastrophic blasts inflicted by terrorists?
Ten days after the terrorist attacks on the twin towers,structural engineers from the University at Buffalo
and the Multidisciplinary Center for Earthquake Engineering Research(MCEER)headquartered at UB
traveled to ground zero as part of a project funded by the National Science Foundation.Visiting the site as
part of an MCEER reconnaissance visit,they spent two days beginning the task of formulating ideas about
how to design such structures arid to search for clues on how to do so in buildings that were damaged but still
are standing.
"Our objective in visiting ground zero was to go and look at the buildings surrounding the World Trade
Center,those buildings that are still standing,but that sustained damage,"said M.Bruneau,Ph.D."Our im-
mediate hope is that we can develop a better understanding as to why those buildings remain standing,while
our long-term goal is to see whether earthquake engineering technologies can be married to existing technolo-
gies to achieve enhanced performance of buildings in the event of terrorist attacks,"he added.
Photographs taken by the investigators demonstrate in startling detail the monumental damage inflicteed
on the World Trade Center towers and buildings in the vicinity.One building a block away from the towers
remains standing,but was badly damaged."This building is many meters away from the World Trade Center
and yet we see a column there that used to be part of that building,"explained A.Whittaker,Ph.D."The
column became a missile that shot across the road,through the window arid through the floor."
The visit to the area also revealed some surprises,according to the engineers.For example,the floor
framing system in one of the adjacent buildings was quite rugged,allowing floors that were pierced by tons of
falling debris to remain intact. " Highly redundant ductile（有延展性的）framing systems may provide a sim-
pie,but robust strategy for blast resistance,"he added.Other strategies may include providing alternate paths
for gravity loads in the event that a load一bearing column fails."We also need a better understanding of the
mechanism of collapse,"said A.Whittaker."We need to find out what causes a building to collapse and how
you can predict it."
A.Reinhorn,Ph.D.noted that"Earthquake shaking has led to the collapse of many buildings in the
past.It induces dynamic response and extremely high stresses and deformations in structural components.So-
lutions developed for earthquake-resistant design may be directly applicable to blast engineering and
terrorist-resistant design.Part of our mission now at UB is to transfer these solutions and to develop new ones
where none exist at present."
The question raised in the first paragraph is one_______.
A:that was asked by structural engineers a month ago
B:that is too difficult for structural engineers to answer even now
C:that was never imagined before the terrorist attack
D:that terrorists are eager to find a solution to
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The Greatest Mystery Of Whales
The whale is a warm-blooded,air-breathing animal,giving birth to its young alive,
sucking them一and,like all mammals,originated on land.There are many_________
(1)of this. Its front flippers（鳍状肢）,used for steering and stability,are traces of feet.
Immense strength is_________(2)into the great body of the big whales,and in
fact most of a whale's body is one gigantic muscle.The blue whale's pulling strength has
been estimated_________(3)400 horsepower. One specimen was reported to have
towed（拖）a whaling vessel for seven hours at the_________(4)of eight knots （节）.
An angry whale will_________(5)a ship.Afamous example of this was the fate
of whaler Essex,_________(6)was sunk off the coast of South America early in the
last century. More recently,steel ships have_________(7) their plates buckled（使弯
曲）in the same way. Sperm whales（抹香鲸）were known to seize the old-time
whaleboats in their jaws and crush them.
The greatest_________(8)of whales is their diving ability.The sperm whale dives
to the bottom for his_________(9) food, the octopus（章鱼）.In that search he is
known to go as far down as 3, 200 feet,where the_________(10)is 1,400 pounds,to
a square inch.Doing so he will_________(11)underwater long as one hour. Two
special skills are involved in this:storing up enough_________(12)(all whales are air-
breathed)and tolerating the great change in pressure.Just how he does it scientists have
not_________(13).It is believed that some of the oxygen is stored in a special
_________(14)of blood vessels,rather than just held in the lungs.And it is believed
that a special kind of oil in his head is some sort of compensating mechanism that
_________(15)adjusts the internal pressure of his body.But since you can't bring a
live whale into the laboratory for study,no one knows just how these things work.
_________(12)
A:heat
B:energy
C:food
D:oxygen
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第三篇
Cell Phones : Hang Up or Keep Talking?
Millions of people are using cell phones today.In many places it is actually considered unusual not to
use one.In many countries,cell phones are very popular with young people.They find that the phones are
more than a means of communication一having a mobile phone shows that they are cool and connected.
The explosions around the world in mobile phone use make some health professionals worried.Some
doctors are concerned that in the future many people may suffer health problems from the use of mobile
phones.In England,there has been a serious debate about this issue.Mobile phone companies are worried
about the negative publicity of such ideas.They say that there is no proof that mobile phones are bad for your
health.
On the other hand,why do some medical studies show changes in the brain cells of some people who use
mobile phones?Signs of change in the tissues of the brain and head can be detected with modern scanning
（扫描）equipment. In one case , a traveling salesman had to retire at a young age because of serious memory
Loss.He couldn't remember even simple tasks.He would often forget the name of his own son.This man used
to talk on his mobile phone for about six hours a day,every day of his working week,for a couple of years.
His family doctor blamed his mobile phone use,but his employer's doctor didn't agree.
What is it that makes mobile phones potentially harmful?The answer is radiation.High-tech machines
can detect very small amounts of radiation from mobile phones.Mobile phone companies agree that there is
some radiation,but they say the amount is too small to worry about.
As the discussion about their safety continues,it appears that it's best to use mobile phones less often.
Use your regular phone if you want to talk for a long time.Use your mobile phone only when you really need
it.Mobile phones can be very useful and convenient,especially in emergencies.In the future,mobile phones
may have a warning label that says they are bad for your health.So for now,it's wise not to use your mobile
phone too often.
People buy cell phones for the following reasons EXCEPT that__________.
A:they're convenient
B:they're useful
C:they're popular
D:they're cheap
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The Northern Lights
The Sun is stormy and has its own kind of weather It is so hot and active that even the Sun's gravity cannot hold its atmosphere in check!Energy flows away from the Sun toward the Earth in a stream of electrified particles that move at speeds around a million miles per hour. These particles are called plasma,and the stream of plasma coming from the Sun is called the solar wind. The more active the Sun,the stronger the solar wind.
The solar wind constantly streams toward the Earth,but don't worry because a protective magnetic field surrounds our planet.The same magnetic field that makes your compass point north also steers the particles from the Sun to the north and south poles.The charged particles become trapped in magnetic belts around the Earth. When a large blast of solar wind crashes into the Earth's magnetic field,the magnetic field first gets squeezed and then the magnetic field lines break and reconnect.
The breaking and reconnecting of the magnetic field lines can cause atomic particles called electrons trapped in the belts to fall into the Earth's atmosphere at the poles. As the electrons fall to the Earth,they collide with gas molecules in the atmosphere,creating flashes of light in the sky. Each atmospheric gas glows a different color. Oxygen and nitrogen glows red and green and nitrogen glows violet-purple. As these various colors glow and dance in the night sky,they create the Northern Lights and the Southern Lights.
Watching auroras is fun and exciting,but normally you can only see them in places far north like Alaska and Canada. The movement of the aurora across the sky is usually slow enough to easily follow with your eyes but they can also pulsate,flicker,or even move like waves.During solar maximum,auroras are seen as far south as Florida,even Mexico!
Auroras often seem to be very close to the ground,but the lowest aurora is still about 100 kilometers above the ground,a distance much higher than clouds are formed or airplanes can fly. A typical aurora band can be thousands of kilometers long,a few hundred kilometers high,but only a few hundred meters thick.
We hope you are able to travel to far north places like the Arctic Circle and see the Northern Lights at least once during your lifetime. We know you will never forget it!
The auroras are formed when the electrons falling into the Earth's atmosphere at the poles and colliding with gas molecules in the atmosphere.
A: Right
B: Wrong
C: Not mentioned
