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【29】
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Part A
Directions: Read the following four texts. Answer the questions below each text by choosing A, B, C or D . Mark your answers on ANSWER SHEET 1.
British cancer researchers have found that childhood leukaemia is caused by an infection and clusters of cases around industrial sites are the result of population mixing that increases exposure. The research published in the British Journal of Cancer backs up a 1988 theory that some as yet unidentified infection caused leukaemia--not the environmental factors widely blamed for the disease.
"Childhood leukaemia appears to be an unusual result of a common infection," said Sir Richard Doll, an internationally-known cancer expert who first linked tobacco with lung cancer in 1950. "A virus is the most likely explanation. You would get an increased risk of it if you suddenly put a lot of people from large towns in a rural area, where you might have people who had not been exposed to the infection." Doll was commenting on the new findings by researchers at Newcastle University, which focused on a cluster of leukaemia cases around the Sellafield nuclear reprocessing plant in Cumbria in northern England. Scientists have been trying to establish why there was more leukaemia in children around the Sellafield area, but have failed to establish a link with radiation or pollution. The Newcastle University research by Heather Dickinson and Louise Parker showed the cluster of cases could have been predicted because of the amount of population mixing going on in the area, as large numbers of construction workers and nuclear staff moved into a rural setting. "Our study shows that population mixing can account for the (Sellafield) leukaemia cluster and that all children, whether their parents are incomers or locals, are at a higher risk if they are born in an area of high population mixing," Dickinson said in a statement issued by the Cancer Research Campaign, which publishes the British Journal of Cancer.
Their paper adds crucial weight to the 1988 theory put forward by Leo Kinlen, a cancer epidemiologist at Oxford University, who said that exposure to a common unidentified infection through population mixing resulted in the disease.
Who first hinted at the possible cause of childhood leukaemia by infection？
The best statement of the main idea of the passage is that ______.
【31】
听力原文：M: Hi, Claire. How does it feel to be back on campus？
W: Gee, Hi, well, to tell you the truth, I have mixed feelings.
M: Oh, why？
W: I have this great summer job that I really hated to leave. I worked at the wild life research center in Maryland.
M: That makes sense for a genetic major. What did you do？ Clean the cages？
W: This is a wild life center, not a zoo. This place breeds endangered species and tries to prepare them for life in the wild.
M: You mean the endangered species like the tiger and the panda？
W: Well, endangered species, yes. But not tigers or pandas. I work with whooping cranes and sandhill cranes. I taught the baby crane how to eat and drink, and I help the vets to give medical check-ups. M: I can see it was hard to leave that job. But how did you teach a bird how to eat and drink？
W: We covered ourselves up with cloth and used puppets made out of stuffed cranes to show the baby chicks what to do. Then the chicks copied what the puppets did.
M: Cloth？ Puppets？ Sounds like fun.
W: It was. The cloth and puppets are the key tools. We all covered ourselves up, the scientists, the vets, the junior staff, everybody. You see, baby cranes will become attached to their caretakers.
M: So if the caretaker is a person, the crane will stay in places where people are.
W: Yeah. And their chances for survival aren't very good. But by covering ourselves and using cloth and puppets the chicks are more likely to seek out other birds rather than people. And their transition to the wild has a better chance of being successful.
M: A chance of being successful？ Hasn't this been done before？
W: It's been done with sandhill cranes and everyone is optimistic about its work with whooping cranes too.
M: If this works, it should increase the number of cranes in the wild.
W: Yeah. It's exciting, isn't it？
Why dues the woman say she has mixed feeling？
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