24-15 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, scientists hypothesize that in high salt environments the antibiotic becomes ineffective at killing harmful bacteria.>>

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Which of the following, if it were obtained as an experimental result, would most decisively undermine the scientists’ hypothesis?>>

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1. Healthy lungs in which the salt concentration of the airway-surface fluid has been substantially increased are able to reestablish their normal salt concentration within a relatively short period of time.>>
2. The antibiotic produced by the lungs is effective at killing harmful bacteria even when salt concentrations are below levels typical of health lungs.
3. The salt concentration of the airway-surface fluid in the lungs of people who suffer from cystic fibrosis tends to return to its former high levels after having been reduced to levels typical of healthy lungs.
4. The lungs of people who suffer from cystic fibrosis are unable to fight off harmful bacteria even when the salt concentration is reduced to levels typical of healthy lungs.
5. The salt concentration in the airway-surface fluid of people whose lungs produce lower-than-average amounts of the antibiotic is generally much lower than that typical of healthy lungs.

I choose D ,but the answer is E

why????????????????????

题目是削弱啊

削弱＂ ineffective ＂这个词

谁能给讲讲这道题的逻辑关系吗？为什么选D？我选了C。。

我记得这道题在gwd1-9中出现过，但现在找不到了，所以没办法查之前的讨论。。

我的理解是D表达的意思为:

即使恢复到健康肺的含盐度,患有cystic fibrosis的肺还是不能抵抗有害菌.

也就是说,可能是肺的问题,而不一定是盐度问题,

所以削弱原文说就是因为盐度问题导致杀菌无效.

逻辑分析就是:原文定义出一种原因,选项说出另外的可能性来削弱原文.

好比两个人吵架,你说是盐度高不行对吧,那好,那我说盐度恢复了,也还是不行,来反驳你的见解.

不知道我这么理解合适吗?

至于你说的C,原文关键在于杀菌是否有效,C很绕口,但是关于杀菌的问题一点没提,就说了浓度上上下下,,,,无关.