Section B

　　Directions: There are 2 passages in this section. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A), B), C) and D). You should decide on the best choice and mark the corresponding letter on Answer Sheet 2 with a single line through the centre.

　　Passage One

　　Questions 52 to 56 are based on the following passage.

　　It happened one morning 20 years ago. British scientist Alec Jeffrey stumbled upon DNA fingerprinting: He identified the patterns of genetic(基因的) material that are unique to almost every individual. His discovery changed everything from the way we do criminal investigations to the way we decide family law. But the professor of genetics at the University of Leicester, UK, is still surprised, and a bit worried, by the power of the technology he released upon the world.

　　The patterns within DNA are unique to each individual, except identical twins, who share the same pattern. The ability to identify these patterns has been used to convict murderers and to clear people who are wrongly accused. It is also used to identify the victims of war and settle disputes over who is the father of a child.

　　Jeffrey said he and his colleagues made the discovery by accident while tracking genetic variations. But, within six months of the discovery, genetic fingerprinting had been used in an immigration case, to prover that an African boy really was his parents’son. In 1986, it was used for the first time in a British criminal case: It cleared one suspect after being accused of two rapes and murders and helped convict another man.

　　DNA testing is now very common. In Britain, a national criminal database established in 1995 now contains 2.5 million DNA samples(樣本). The U.S. and Canada are devloping similar systems. But there are fears about the stored DNA samples and how they could be used to harm a person’s privacy. That includes a person’s medical history, racial origin or psychological profile. “There is the long-term risk that people can get into these samples and start getting additional information about a person’s paternity or risk of disease,” Jeffrey said.

　　DNA testing is not an unfailing proof of identity. Till, it is considered a reasonably reliable system for determining the things it is used for. Jeffrey estimates(估計) the probability of two individuals’DNA profiles maching in the most commonly used tests at between one in a billion or one in a trillion.

　　52. The passage is mainly about .

　　A) the discovery of fingerprinting by Jeffery

　　B) the practice of fingerprinting in court

　　C) the fingerprinting in the present situation

　　D) the merits and demerits of fingerprinting

　　53.The phrase “stumbled upon”(Line 1, Para. 1) is closest in meaning to “ ”.

　　A) discovered after great efforts B) found out quite by chance

　　C) amazed and confused by D) invented in experiments

　　54. The significance of the DNA fingerprinting is that .

　　A) the patterns of genetic material are unique in everybody

　　B) it can be used to identify criminals by testing their DNAs

　　C) DNA testing can tell the wated information of some people

　　D) DNA testing can help those who are wrongly accused

　　55. The British DNA database is established to .

　　A) find the identical DNA profiles B) help criminal investigations

　　C) store people’s personal information D) treat people of potential diseases

　　56.By saying“DNA testing is not an unfailing proof of identity”, the author means .

　　A) DNA testing can be wrong in its practices

　　B) there are identical patterns of genetic material

　　C) many people have the identical DNA profiles

　　D) DNA testing are endangering people’s privacy