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"I have great confidence that by the end of the decade we'll know in vast detail how cancer cells arise," says microbiologist Robert Weinberg, an expert on cancer. "But." he cautions, "some people have the idea that once one understands the causes, the cure will rapidly follow. Consider Pasteur. He discovered the causes of many kinds of infections, but it was fifty or sixty years before cures were available."

This year, 50 percent of the 910,000 people who suffer from cancer will survive ai least five years. In the year 2000. the National Cancer Institute estimates, that figure will be 75 percent. For some skin cancers, the five-year survival rate is as high as 90 percent. But other survival statistics are still discouraging-13 percent for lung cancer. and 2 percent for cancer of the pancreas(胰腺)。

With as many as 120 varieties in existence, discovering how cancer works is not easy. The researchers madegreat progress in the early 1970s. when they discovered that oncogenes. which are cancer-causing genes (基因), are inactive in normal cells. Anything from cosmic rays to radiation to diet may activate a dormant oncogene. but how remains unknown. If several oncogenes are driven into action the cell. unable to turn them off. becomes cancerous.

The exact mechanisms involved are still mysterious, but the likelihood that many cancers are initiated ai the level of genes suggests that we will never prevent all cancers. "Changes are a normal pan of the evolutionary process." says oncologist William Hayward. Environmental factors can never be totally eliminated; as Hayward points out, "We can't prepare a medicine against cosmic rays. "

The prospects for cure.though still distant, are brighter.

"First we need io understand how the normal cell controls itself. Second,we have to determine whether there are a limited number of genes in cells which are always responsible for al least pan of the trouble. If we can understand how cancer works. we can counteract its action."

1.Robert Weinberg warns that the discovery of the causes or cancer cells won't necessarily lead to_______________________.

2.It is not easy to rind out how cancer works because__________________.

3.Once oncogenes in cells are at work.the cell will become_______________________.

4.By saying "We can't prepare a medicine against cosmic rays", William Hayward implies that it is impossible to avoid che impact of_______________________.

5.Provided that the mechanisms of cancer are found out we are able to_______________________.

答案：

1.[the rapid discovery of its cure]

[定位]根据题干中的Robert Weinberg和causes查找到第1段第2句。

解析：题干warns对应原文cautions，转折词But表明Robert Weinberg认为，这些人的想法是错的，即他并不认为找到了癌症的成因就能很快的找到该癌症的治疗方法(the rapid discovery of its cure)。

2.[there are 120 varieties of cancer in existence]

[定位]根据题干中的how cancer works查找到第3段第1句。

解析：原文中的discovering对应题干中的find out，填入的内容需在句首with...中找, because后接完整的从句，因此需补上there are。

3.[cancerous]

[定位]根据题干中的oncogenes查找到第3段最后一句。

解析：题干中的are at work和原文中的are driven into action属于同义替换，因此照搬原文becomes后的形容词cancerous即可。

4.[environmental factors]

[定位]根据题干引号内容查找到第4段最后一句。

解析：原文该句的前一个分句的内容说，环境因素永远无法彻底消除，而接下来海沃德的话也说明这一点。题干中that从句是对该段末句的后一个分句的近义改写。对比原文与题干，可知environmental factors为本题答案。

5.[counteract its action]

[定位]末段末句。

解析：题干中Provided引导条件句，相当于If;被动句the mechanisms of cancer are found out和原文understand howcancer works表达了相同的意思，在这种假设条件下，原文所说的结果是we can counteract its action，故counteractits action为答案。

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