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.

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

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.

始终不能想得很明白，跟原来那道题题干相同问法不同

原为支持5－26；11－21题目，健康的肺产生自然的抗生素保护它们不被空气中的细菌感染。人们有c并的不能对付这些细菌，尽管它们的肺产生正常的抗生素，有c病的人的肺的表面流动的液体含盐量异常的高，科学家假设高盐量使得抗生素不能有效杀死细菌。

问破坏假设，e 高盐量根本很少抗生素产生～即破坏假设～d得c病得人不能杀死细菌甚至含盐量降到正常

可能受原题影响，我觉得de都有点意思呢～～～