21. A. run 　　　　　　　　　　　　　 B. pass　　　　　　　　　　　　　　　　 C. move　　　　　　　　　　　　　　　　　　　　 D. travel

55. The aim of the passage is to ______.

　　 A. praise Ian Findlay for his work　　　

　　 B. report a piece of interesting news

　　 C. inform us of the wide use of DNA testing　

　　 D. tell us a recent improvement in DNA testing

54. The last paragraph suggests that ______.

A. the immediate adopting of the technology may cause mistakes

B. the public have acknowledged the new testing technology

C. it is safe to put the new technology into use now

D. Dr Findlay is quite sure of his new technology

53. According to Ian Findlay, the new technology can ______.

A. help to keep DNA evidence fresh for decades and even centuries

B. make the process of DNA testing much more simplified

C. help to pick up DNA identities more easily

D. be widely used in five years at most

52. The underlined word" validated" means ______.

　　　　 A. confirmed　 　　　　　 B. imagined　 　　　　　　　 C. supposed　 　　　　　　 D. criticized

51. The main advantage of the new technology is that ______.

A．a single cell can identify an individual

　 B．it has brought down the cost of DNA testing

　　　　 C．a higher level of accuracy can be acquired with a single cell

　　　　 D．it needs less than 200 cells to gain a certain level of accuracy

50. In this passage, the writer mainly　　　 .

A. describes two types of people　　　　

B. laughs at the unhappy people

C. suggests ways to help the unhappy　　

D. tells people how to be happy in life

C

An Australian-based scientist announced yesterday he had made a step forward in forensic (用于法庭的) DNA testing so that an individual can be identified by a single cell.　　　

Ian Findlay, from the Australian Genome Research Facility at the University of Queensland, said current DNA testing required 200 to 500 cells to gain a similar level of accuracy. "What we have done has brought that down to one cell," Dr Findlay said after releasing details of his DNA testing technique at a Sydney conference.　　

The technology could allow investigators to pick up DNA identities from plastic cards and even build up a complete history of the people who have handled a paper document.

"You'd have to wear a space suit to stop yourself from leaving traces. You can identify cells on the paper, so you can work out where it's come from and who's touched it,” he said.

The technique could also be used to trace the thrower of a punch(打孔)from cells left behind on the skin of their victim. Even the wearing of latex(橡胶)gloves would not help: small cells can pass through the gloves, and the constant flow of genetic material given off by the human body would leave further evidence.

"We gained a skin cell from a document dating back 30 years and managed to gain a DNA fingerprint. DNA evidence can remain fresh for decades, perhaps even centuries," Dr Findlay said.　 "The potential for this technology to solve unsolved crimes is great, "he said.　　

But Dr Findlay, named scientist of the year in 1998 by the European Society of Human Genetics, said the new testing needed to be scientifically validated, which would take up to five years.　　　

He said, "There are serious consequences taking on technologies too early. The public has to be sure that they have the utmost confidence in the security and court systems."

49. If such unhappy persons insist on keeping the habit, the author suggests that people should 　　　.

A. prevent any communication with them

B. show no respect and politeness to them

C. persuade them to recognize the bad effects

D. quarrel with them until they realize the mistakes

48. We can conclude from the passage that 　　　

A. we should pity all such unhappy people

B. such unhappy people are dangerous to social life

C. people can get rid of the habit of unhappiness

D. unhappy people can not understand happy persons

47. The underlined phrase “sour the pleasure of society” most nearly means “　　 ”.

A. have a good taste with social life　　　　

B. make others unhappy

C. tend to scold others openly　　　　　　

D. enjoy the pleasure of life