It is a wise father that knows his own child, but today a man can boost his paternal (fatherly) wisdom — or at least confirm tha

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问题     It is a wise father that knows his own child, but today a man can boost his paternal (fatherly) wisdom — or at least confirm that he’s the kid’s dad. All he needs to do is shell out $30 for paternity testing kit (PTK) at his local drugstore — and another $120 to get the results.
    More than 60,000 people have purchased the PTKs since they first become available without prescriptions last years, according to Doug Fogg, chief operating officer of Identigene, which makes the over-the-counter kits. More than two dozen companies sell DNA tests directly to the public, ranging in price from a few hundred dollars to more than $2,500.
    Among the most popular: paternity and kinship testing, which adopted children can use to find their biological relatives and families can use to track down kids put up for adoption, DNA testing is also the latest rage among passionate genealogists — and supports businesses that offer to search for a family’s geographic roots.
    Most tests require collecting cells by webbing saliva (唾液) in the mouth and sending it to the company for testing. All tests require a potential candidate with whom to compare DNA.
    But some observers are skeptical. "There is a kind of false precision being hawked by people claiming they are doing ancestry testing," says Trey Duster, a New York University sociologist. He notes that each individual has many ancestors — numbering in the hundreds just a few centuries back. Yet most ancestry testing only considers a single lineage (世系), either the Y chromosome (染色体) inherited through men in a father’s line or mitochondrial (线粒体) DNA, which is passed down only from mothers. This DNA can reveal genetic information about only one or two ancestors, even though, for example, just three generations back people also have six other great-grandparents or, four generations back, 14 other great-great-grandparents.
    Critics also argue that commercial genetic testing is only as good as the reference collections to which a sample is compared. Databases used by some companies don’t rely on data collected systematically but rather lump together information from different research projects. This means that a DNA database may have a lot of data from some regions and not others, so a person’s test results may differ depending on the company that processes the results.
What is Skeptical observers’ opinion on ancestry testing?

选项 A、It fails to trace distant ancestors.
B、It rebuilds reliable bloodlines.
C、It contains fully genetic information.
D、It fails to achieve the claimed accuracy.

答案D

解析 根据题干中的Skeptical observers可将本题出处定位于第五段首句。该句提到,但是有些观察家们持怀疑态度。第二句提到,纽约州立大学的社会学家Troy Duster说,“那些声称他们可以进行血液检测的人兜售的是虚假的准确性”,这说明,持怀疑态度的观察者们认为基因检测的结果不准确。故答案为[D]。第五段末句说的是这些人所提供的血液检测只能追踪一两个祖先,不能追踪其他的祖先,说的是祖先的数量问题,故排除强干扰项[A]。[B]“复原可靠的血统”属于理解原文错误的情况下设计的选项。[C]是根据第五段第四句所设的干扰项。
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