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 theEnvironment 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.
