下面的短文后有2项测试任务：(1)第23～26题要求从所给的6个选项中为第2～5段每段选择1个最佳标题；(2)第27～30题要求从所给的6个选项中为每个句子确定1个最佳选项。 Screen Test 1
Every year millions of women are screened with X-rays to pick up signs of
breast cancer, ff this happens early enough, the disease can often be treated
successfully. According to a survey pub- lished last year, 21 countries have
screening programmes. Nine of them, including Australia, Canada, the US and
Spain, screen women under 50. 2 But the medical benefits
of screening these younger women are controversial, partly because the radiation
brings a small risk of inducing cancer. Also, younger women must be given higher
doses of X-rays because their breast tissue is denser. 3
Researchers at the Polytechnic University of Valencia analyzed the effect
of screening more than 160,000 women at 11 local clinics. After estimating the
women’s cumulative dose of radiation, they used two models to calculate the
number of extra cancers this would cause. 4 The
mathematical model recommended by Britain’s National Radiological Protection
Board (NRPB) predicted that the screening programme would cause 36 cancers per
100,000 women, 18 of them fatal. The model preferred by the UN Scientific
Committee on the Effects of Atomic Radiation led to a lower figure of 20
cancers. 5 The researchers argue that the level of
radiation-induced cancers is "not very significant" compared to the far larger
number of cancers that are discovered and .treated. The Valencia programme, they
say, detects between 300 and 450 cases of breast cancer in every 100,000 women
screened. 6 But they point out that the risk of women
contracting cancer from radiation could be reduced by between 40 and 80 percent
if screening began at 50 instead of 45, because they would be exposed to less
radiation. The results of their study, they suggest, could help "optimize the
technique" for breast cancer screening. 7 "There is a
trade-off between the diagnostic benefits of breast screening and its risks,"
admits Michael Clark of the NRPB. But he warns that the study should be
interpreted with caution. "On the basis of the current data, for every 10
cancers successfully detected and prevented there is a risk of causing one later
in life. That’s why radiation exposure should be minimized in any screening
programme. "
A. Harm Screening May Do to a Younger Woman B.
Investigating the Effect of Screening C. Effects Predicted by
Two Different Models D. Small Risk of Inducing Cancers from
Radiation E. Treatment of Cancers F. Factors
That Trigger Cancers Paragraph 2 ______.