GWD5-26

GWD5-Q26:

Healthy lungs produce a natural antibiotic that protects them from infection by routinely killing harmful bacteria on airway surfaces.  People 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.
        正确

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.

c是无因无果，正确。可是B哪里不对呢？

原文说

      健康的肺会产生抗体对抗细菌。但是有CF的人不能够对抗细菌，尽管他们的肺一样会产生抗体。患有CF的人的肺里有不正常的高的盐的含量。科学家假设，是因为高盐导致这种抗体无效。问加强。

A说含盐量被人工提高了，他会恢复正常。（无关）

B说抗体能够在低盐的环境下杀死细菌。（文中要加强的是 是由于患有CF的组织在高盐的环境下导致抗体不能够杀细菌。注意我们讨论的是患有CF的人的肺，所以低盐下杀的死杀不死，不是我们讨论的范围。）

C说当把患有CF的组织放在正常的盐的浓度，这个阻止可以抵抗细菌。（这个就是有关）

D说很多肺部感染可以用什么方法治。（无关）

E说高盐有抗菌的作用在很多情况下（无关么）