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People from large families have an increased risk of stomach cancer, suggests a study that followed more than 7,000 Japanese-Ame

admin2013-06-02  17
问题     People from large families have an increased risk of stomach cancer, suggests a study that followed more than 7,000 Japanese-American men for 28 years.
    The study concluded that family size had a major influence on the development of stomach cancer linked to the bacterium Helicobacter pylori (幽门螺杆菌), and that younger siblings (兄弟，姐妹，同胞，同属) from large families were especially prone to the most common form of stomach cancer.
    H. pylori lives in the mucous (黏液的) layer of the stomach and is associated with peptic ulcers (消化器官溃疡) and stomach cancer. It’s estimated that half of the world’s population carries H. pylori in the stomach. It can be transmitted orally from person to person or through contact with human feces (粪便).
    The study found that men who carried certain strains of H. pylori in their stomachs and had seven or more siblings had more than twice the risk of developing stomach cancer, compared to men with the same H. pylori strains who had one to three siblings.
     The findings are published in the January 16 online issue of the journal Public Library of Science Medicine.
     "This is a very carefully controlled study that clearly shows that there are factors in early childhood that affect the risk of developing cancer many decades later," study leader Dr. Martin J. Blaser, professor and chairman of the Department of Medicine, and professor of microbiology at New York University Medical Center and School of Medicine, said in a prepared statement.
     "That early childhood events affect the risk of cancers occurring in old age is remarkable, and this may be a model for other cancers," Blaser said. He said that younger children in large families may acquire H. pylori from older siblings at a time when the younger children’s immune systems are still developing. This, in combination with the fact that the bacterium is already adapted to a genetically related person, means the younger children may have a more virulent H. pylori population in the stomach than if they’d acquired the germ from a non-relative.  
Which of the following statements can best generalize the passage?
选项 A、Family size may determine stomach-cancer risk.
B、Family size may move stomach-cancer risk.
C、The study may follow more than 7,000 Japanese-American men for 28 years.
D、People from small families have an increased risk of stomach cancer.
答案A
解析 这是一篇介绍科学实验的文章，主要介绍这项研究所得出的结论：家庭的大小决定家庭成员得胃癌的机率。文章在一开始就表明了这项研究的结论，然后逐一解析，对结论进行说明。这样，只有A项符合题意。
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