GWD5-Q26

francoiswang

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.

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，为什么B不对呢，B不是说在低盐度的环境下，可以杀死细菌吗，不是正加强了结论。NN们请指教啊




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，为什么B不对呢，B不是说在低盐度的环境下，可以杀死细菌吗，不是正加强了结论。NN们请指教啊

francoiswang

怎么没人理啊~自己先顶一下

chengcheng0820

我认为是，B错误在于说低盐的环境下能杀死细菌 那么有可能在高盐的环境下也能杀死细菌

葛佳

个人愚见：
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.


实验组和对照组
Fact1: high salt concentration ----》 影响
要找出对照组 ： high -------反面normal level  【high-----非high】
A--?B  SUPPORT 非A-?非B
如果分析有错误请指出

sunli2829

已知事实：患有CF病的人无法通过分泌的抗生素杀死细菌；
现象：患有CF病的人肺中盐的含量高；
结论：肺中的高含量盐导致抗生素无效；
显然C答案在现象和结论构架了合理推断的“桥”，它说如果CF病患者肺中盐含量比较低的话，肺组织就可以有效的杀死了细菌。显然在没有改变CF患者其他任何因素，只改变了盐含量而导致了肺组织从无效到有效，那么盐含量就是决定CF病人肺组织抗生素是否有效的因素；
B答案--这种抗生素在低盐含量下可以杀死细菌，并没有提到不能在高盐含量下就不能杀死细菌。

fangsigaoa

请问A为什么不对呢~~~~~~

sdcar2010

请问A为什么不对呢~~~~~~

-- by 会员 fangsigaoa (2011/6/12 18:56:37)

The main conlcusion is about the patient, not normal people. Thus A), which deals with normal people, would not support the main conclusion.

fangsigaoa

请问A为什么不对呢~~~~~~

-- by 会员 fangsigaoa (2011/6/12 18:56:37)

The main conlcusionis about the patient, not normal people. Thus A), which deals with normal people, would not support the main conclusion.

-- by 会员 sdcar2010 (2011/6/12 19:49:28)

恩~感动，谢谢牛牛~~~

violetmoony

刚也看到这题，补充一下：
认为B的对照组选择不当是因为没有把有CF的lung加入到对照中。如果问题在于CF病产生了其他东西抑制了抗体，而不是高盐的原因，那么B是证明不了问题的。按B的方法是得不出正确结论的。
A是说盐浓度会自我调节，无关选项。

lycking

B 开头是a sample不能代表普遍结论。一般不选。XDF的解释。这个方法不严密，但挺有用的。