gwd-5-26

braveMBA

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 a0.irway 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?

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

答案选c,不知道d为啥错，各位帮忙看看

leadership

The hypothesis is about the effects of high salt concentration vs. normal salt concentration.  B talks about "an unusually low concentration of salt", and therefore is irrelevant.

sammen

D，我认为是无关啊。因为这个题目的结论是什么？scientists hypothesize that the high salt concentration is what makes the antibiotic ineffective这个是结论，support的话要紧抓这个。文章的推倒是fluid含高盐＋抗生物质不能正常工作＝》高盐影响。是个A＝》B的过程。而C说的是正常盐＝》可以工作，这是个非B＝》非A的过程，所以加强了。