49. The underlined word “activity” is most closely related to the word(s) _____.

　 A. cloud　　　　　 B. lightning strikes　　　　 C. lightning flashes　　　　 D. thunderstorms

48. What is TRUE about lightning according to the passage?

　 A. Only a small number of lightning flashes occur on earth.

　 B. Lightning flashes usually jump from one cloud to another.

　 C. Lightning travels 5 times faster than thunder.

　 D. There are far more lightning strikes occurring on earth than we can imagine.

47. We believe that lightning is a downward motion because_______.

　 A. we were taught so by our parents from our childhood.

　 B. we are taken in by our sense of vision.

　 C. it is a common natural sight.

　 D. it is a truth proved by science.

46. Accodring to the author, in the area of the Central Valley____.

　 A. rains usually come without thunder and lightning.

　 B. it is usually dry in April

　 C. children pay no attention to the two natural wonders.

　 D. parents are not interested in thunder an lightning.

45. It can be concluded from the passage that ________.

　 A. safety screens are of poor quality　　　

B. working at a VDU for a long time is good for one’s health

　 C. more and more British offices will use word processors

　 D. British companies will need fewer and fewer managers

B

Although April did not bring us the rains we all hoped for, and although the Central Valley doesn’t generally experience the sound and lightning that can go with those rains, it’s still important for parents to be able to answer the youthful questions about thunder and lightning.

The reason these two wonders of nature are so difficult for many adults to explain to children is that they are not very well understood by adults themselves. For example, did you know that the lightning we see flashing down to the earth from a cloud is actually flashing up to a cloud from the earth? Our eyes trick us into thinking we see a downward motion when it’s actually the other way around. But then, if we believed only what we think and we see, we’d still insist that the sun rises in the monring and sets at night.

Most lightning flashes take place inside a cloud, and only a relative few can be seen jumping between two clouds or between earth and a cloud. But, with about 2,000 thunderstorms taking place above the earth every minute of the day and night, there’s enough activity to produce about 100 lightning strikes on earth every second.

Parents can use thunder and lightning to help their children learn more about the world around them. When children understand that the light of the lightning flashing reaches their eyes almost at the same moment, but the sound of the thunder takes about 5 seconds to travel just one mile, they can begin to time the interval(间隔) between the flash and the crash to learn how close they were to the actual spark(闪光).

44. Which of the following statements is NOT true?

　 A. There are both advantages and disadvantages in using a word processor.

　 B. The British companies care much for the health of the people using word processors.

　 C. The technology in the field of computers has been greatly advanced over the last ten years.

　 D. Using word processors, secretaries can get more time to do more interesting work for their bosses.

43. It is implied but not directly stated in the passage that with the use of word processors _________.

　 A. some secretaries will lose their jobs　

　 B. daily jobs can be done automatically outside office hours

　 C. medical problems related to work with a VDU have increased greatly

　 D. the British companies will make less money

42. According to the writer, the main feature of the revolution in office work over the last　ten years is __________.

　　 A. the saving of time and money

　　 　 B. the use of computers in small companies

　 　 C. the wide use of word processors　　　　　　　　　

D. the decreasing number of secretaries

41. Ten years ago, smaller companies did not use large computers because_________.

　　　　 A. these companies had not enough money to buy such expensive computers

　 　 B. these computers could not do the work that small computers can do today

　 　 C. these computers did not come onto the market

　 　 D. these companies did not need to use this new technology