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标题: GWD 11-21 [打印本页]

作者: polkme 时间: 2010-9-21 15:57
标题: GWD 11-21
Healthy lungs produce a natural antibiotic that protects them from infection by routinely killing harmful bacteria on airway surfaces.

eople with cystic fibrosis, however, are unable to fight off such bacteria, even though their lungs produce normal amounts of the antibiotic. The fluid on airway surfaces in the lungs of people with cystic fibrosis has an abnormally high salt concentration; accordingly, scientists hypothesize that the high salt concentration is what makes the antibiotic ineffective.

Which of the following, if true, most strongly supports the scientists’ hypothesis?

A.   When the salt concentration of the fluid on the airway surfaces of healthy people is raised artificially, the salt concentration soon returns to normal.
B.   A sample of the antibiotic was capable of killing bacteria in an environment with an unusually low concentration of salt.
C.   When lung tissue from people with cystic fibrosis is maintained in a solution with a normal salt concentration, the tissue can resist bacteria.
D.   Many lung infections can be treated by applying synthetic antibiotics to the airway surfaces.
E.   High salt concentrations have an antibiotic effect in many circumstances.

答案是C,我在做的时候踌躇在B与C之间。请问B错在哪里？

作者: aomeisoft7 时间: 2010-9-21 19:48
健康的肺产生抗生素，能杀死细菌。有cystic的人，尽管肺能产生抗生素，却不能杀死细菌。发现有cystic的人fluid含盐度很高。所以，科学家认为，高盐度造成抗生素ineffective

B 抗生素在低盐度环境里可以杀菌。明显的无关项，题目说的是 high concentration of salt （注意到：低盐度可以杀菌，和高盐度能不能杀菌，没有关系）

C 当有cystic 的人，盐度正常时，就可以杀菌了（明显支持了科学家的看法，是盐度的原因）

作者: shencangbulu 时间: 2010-9-22 10:56
科学家的假设是高盐度造成抗生素inactive,不能正常发挥作用,那么连接点就是盐度高低与杀菌之间的关系

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