In last year’ s Science study, researchers at Johns Hopkins University examined the relationship between stem-cell divisions and

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问题     In last year’ s Science study, researchers at Johns Hopkins University examined the relationship between stem-cell divisions and cancer development. They reported that the higher the number of stem-cell divisions in a given tissue, the higher risk for【C1】______cancer. At the time, they said that their findings suggested "65% of cancer... appears to be explained by the number of stem-cell divisions". That stem-cell activity, the researchers suggested, could explain why some people without【C2】______factors like smoking will still get lung cancers.
    " I was startled by their conclusion," Dr. Yusuf Hannun says, a cancer researcher at Stony Brook University in New York and author of the new Nature study. Hannun and his team【C3】______that the first study assumed that stem-cell division and other environmental factors were【C4】______of each other.
    Hannun’ s team wanted to assess the【C5】______to which stem-cell division or environmental factors contribute to developing the disease. To do this, the researchers looked at a variety of data including epidemiological evidence that people living in different regions have different rates of cancer development. They also looked at cell-mutation patterns【C6】______with certain cancers, as well as mathematical models that helped parse how much a cancer was due to【C7】______factors like cell division versus extrinsic factors like environment or lifestyle.
    The new study reported that while intrinsic factors did have a【C8】______in cancer development, environmental factors had a more【C9】______effect and were responsible for 70% -90% of cancer cases.
    This isn’ t the last study to be published on the topic, but as scientists refine their【C10】______of the many things that can contribute to cancer risk, more information is needed.
    A)argue I)intrinsic
    B)associated J)relation
    C)considering K)risk
    D)derived L)robust
    E)developing M)role
    F)extent N)seizes
    G)full O)understanding
    H)independent
【C8】

选项

答案M

解析 根据空格前的冠词a,可判断本空格应该填一个名词。have a role in意为“在……中起作用”,故答案为M)role(角色,任务)。
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