四、阅读理解。下面有3篇短文,每篇短文后有5道题。请根据短文内容,为每题确定1个选项。
第一篇
Eat to Live
A meager diet may give you health and long life, but it’s not much fun — and it might not even be necessary. We may be able to hang on to most of that youthful vigor even if we don’t start to diet until old age.
Stephen Spindler and his colleagues from the University of California at Riverside have found that some of an elderly mouse’s liver genes can he made to behave as they did when the mouse was young simply by limiting its food for four weeks. The genetic rejuvenation won’t reverse other damage caused by time for the mouse, but could help its liver metabolize drugs or get rid of toxins.
Spindlers team fed three mice a normal diet for their whole lives, and fed another three on half-rations. Three more mice were switched from the normal diet to half-feed for a month when they were 34 months old — equivalent to about 70 human years.
The researchers checked the activity of 11, 000 genes from the mouse livers, and found that 46 changed with age in the normally fed mice. The changes were associated with things like inflammation and free radical production — probably bad news for mouse health. In the mice that had dieted nil their lives, 27 of those 46 genes continued to behave like young genes. But the most surprising finding was that the mice that only started dieting in old age also benefited from 70 per cent of these gene changes.
“This is the first indication that these effects kick in pretty quickly.” say Huber Warner from the National Institute on Aging near Washington D. C.
No one yet knows if calorie restriction works in people as it does in mice, but Spindler is hopeful. “There’s attracting and tempting evidence out there that it will work,” he says.
If it does work in people, there might be good reasons for rejuvenating the liver. As we get older, our bodies are less efficient at metabolizing drugs, for example. A brief period of time of dieting, says Spindler, could be enough to make sure a drug is effective.
But Spindler isn’t sure the trade-off is worth it. “The mice get less disease, they live longer, but they’re hungry,” he says, “Even seeing what a diet does , it’s still hard to go to a restaurant and say: ‘I can only cat half of that’.”
Spindler hopes we soon won’t need to diet at all. His company, Lifespan Genetics in California, is looking for drugs that have the effects of caloric restriction.
31. According to the passage, which of the following is NOT true?
A. Eating less than usual might make us live longer.
B. we go on A diet when old, we may keep healthy.
C. Dieting might not be needed.
D. We have to begin dieting since childhood.
32. Why does the author mention an elderly mouse in paragraph 2?
A. To describe the influence or old age on mice.
B. To illustrate the effect of meager food on mice.
C. To tell us how mice’s liver genes behave.
D. To inform us of the process of metabolizing drugs.
33. What can he inferred about completely normally fed mice mentioned in the passage?
A. They will not experience free radical production.
B. They will experience more genetic rejuvenation in their lifetime.
C. They have more old liver genes to behave like young genes.
D. They are more likely to suffer from inflammation.
34. According to the author, which of the following most interested the researchers?
A. The mice that started dieting in old age.
B. 27 of those 46 old genes that continued to behave like young genes.
C. Calorie restriction that works in people.
D. Dieting that makes sure a drug is effective.
35. According 10 the last two paragraphs, Spindler believes that
A. calorie restriction is very important to young people.
B. seeing the effect of a diet, people will like to eat less than normal.
C. dieting is not a good method to give us health and long life.
D. drugs do not have the effects of calorie restriction.
第二篇
Snowflakes
You’ve probably heard that no two snowflakes are alike. Of course, nobody has ever confirmed that statement by examining every one of the estimated one septillion snowflakes that drift to Earth each year. Still, Kenneth Libbrecht, a professor at the California Institute of Technology, is confident that the statement is true.
Snowflakes aren’t flaky, says Libbrecht. At their basic level, they’re crystalline. The lattice of every snowflake is six-sided in shape. The simplest snow crystals are six-sided flat plates and six-sided columns. Such crystals are common in places where the air is extremely cold and dry. Snow crystals acquire their special beauty when their simple six-sided symmetry blossoms. Under the right conditions, each of the six corners of a crystal sprouts1 what is called an arm. In a matter of minutes, the arms can become highly ornate and give the crystal a star like appearance.
Several factors in the environment affect the shape and growth rate of a snow crystal. One factor is humidity. Crystals grow faster and in more intricate shape as humidity increases. A second factor is air temperature. A snowflake is born when several molecules of water vapor in a cloud land on a speck of dust and freeze to form a simple crystal. As the young crystal bops around in the cloud, it passes through air pockets of varying temperatures. If the crystal passes through a pocket of air that is, say, -15 degrees Celsius, it will grow quickly and sprout six arms says Libbrecht. If the crystal is then tossed into a warmer pocket, one about -100C, the arms tips will stop growing quickly and form six-sided plates. If the crystal then drifts into an even warmer pocket of about -50C, its top and bottom will grow more quickly than its sides and become more column like in shape.
In the course of its life span, a snow-crystal might flutter through many warmer and colder pockets, acquiring a complicated and unique growth history. Such a history will give rise to a snowflake that is unlike any other. Each arm on the snowflake will look exactly like every other one, but the crystal itself will be one of a kind.
Using his cooling tanks, Libbrecht has learned how to create snow crystals of different shapes - plates, columns, needles, etc. Libbrecht has even refined his techniques so that he can make crystals that look highly similar to one another. Still, he lacks the control to manufacture identical twin snowflakes. A slight difference in humidity and temperature can upset the growth profile of a crystal.
36. What does Professor Libbrecht believe to be true?
A. No two snowflakes are exactly the same in shape.
B. Somebody has examined all the snowflakes that fall on Earth.
C. The statement that no two snowflakes are alike is confirmed.
D. None of the above.
37. What do the simplest snow crystals look like?
A. They have six columns.
B. They are flaky.
C. They are cubic in shape.
D. They are six-sided.
38. What are the factors that affect the shape and growth rate of a snow crystal?
A. Humidity and temperature.
B. Water and falling speed.
C. Air and altitude.
D. Both B and C.
39. It can be felt from the description in the 2nd paragraph that the author
A. admires the beauty of the snowflakes.
B. dislikes the changing growth history of the snowflakes.
C. has a particular feeling for those flower-like crystals.
D. likes to compare snowflakes to the stars in the sky.
40. Libbrecht is not able to
A. create snow crystals of different shapes.
B. make crystals that look similar to one another.
C. create snowflakes that era exactly alike.
D. refine his techniques.
第三篇
Ford Abandons Electric Vehicles
The Ford motor company’s abandonment of electric cars effectively signals the end of the road for the technology, analysts say.
General Motors and Honda ceased production of battery-powered cars in 1999, to focus on fuel cell and hybrid electric gasoline engines, which are more attractive to the consumer. Ford has now announced it will do the same.
Three years ago, the company introduced the Think City two-seater car and a golf cart called the THINK or Think Neighhor. It hoped to sell 5,000 cars each year and 10,000 carts. But a lack of demand means only about 1,000 of the cars have been produced, and less than 1,700 carts have been sold so far in 2002.
“The bottom line is we don’t believe that this is the future of environment transport for the mass market,” Tim Holmes of Ford Europe said on Friday. “We feel we have given electric our best shot.”
The Think City has a range of only about 53 miles and up to a six-hour battery recharge time. General Motors’ EVI electric vehicle also had a limited range, of about 100 miles.
The very expensive batteries also mean electric cars cost much more than petrol-powered alternatives. An electric Toyota RAV4 EV vehicle costs over $42,000 in the US, compared with just $17,000 for the petrol version. Toyota and Nissan are now the only major auto manufacturers to produce electric vehicles.
“There is a feeling that battery electric has been given its chance. Ford now has to move on with its hybrid program, and that is what we will be judging them on,” Roger Higman, a senior transport campaigner at UK Friends of the Earth, told the Environment News Service.
Hybrid cars introduced by Toyota and Honda in the past few years have sold well. Hybrid engines offer greater mileage than petrol-only engines, and the batteries recharge themselves. Ford says it thinks such vehicles will help it meet planned new guidelines on vehicle emissions in the US.
However, it is not yet clear exactly what those guidelines will permit. In June, General Motors and Daimler Chrysler won a court injunction, delaying by two years Californian legislation requiring car-makers to offer 100,000 zero-emission and other low-emission vehicles in the state by 2003. Car manufacturers hope the legislation will be rewritten to allow for more low-emission, rather than zero-emission, vehicles.
41. What have the Ford motor company, General Motor’s and Honda done concerning electric cars? A. They have started to produce electric cars.
B. They have done extensive research on electric cars.
C. They have given up producing electric cars.
D. They have produced thousands of electric cars.
42. According to Tim Holmes of Ford Europe, battery-powered cars
A. will be the main transportation vehicles in the future.
B. will not be the main transportation vehicles in the future.
C. will be good to the environment in the future.
D. will replace petrol-powered vehicles in the future.
43. Which auto manufacturers are still producing electric vehicles?
A. Toyota and Nissan.
B. General Motor’s and Honda.
C. Ford and Toyota.
D. Honda and Toyata.
44. According to the eighth paragraph, hybrid cars
A. offer fewer mileage than petrol driven cars.
B. run faster than petrol driven cars.
C. run more miles than petrol driven cars.
D. offer more batteries than petrol driven cars.
45. Which of the following is true about the hope of car manufacturers according to the last paragraph?
A. Low-emission cars should be banned.
B. Only zero-emission cars are allowed to run on motorways.
C. The legislation will encourage car makers to produce more electric cars.
D. The legislation will allow more low-emission to be produced.
参考答案:
31-35 DBDAC
36-40 ADAAC
41-45 CBACD
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