求助，gwd-11-21

knifekelly

Q21:

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

是实在不明白，有两个答案，一个选Ａ，一个选Ｄ

kingsoft

       选C

       原文说高盐浓度导致抗体失效

       选项说正常盐浓度抗体有用

       支持

knifekelly

我当归纳题做了，呵呵，头晕了！

card_mistress

D is incorrect because it basically means that antibiotics are not susceptible to salt, i.e., the synthetic antibiotics, when applied to a surface containing salt, remain effective. This does not strengthen the argument.

Is it A or C??? I can't decide which? Anyone help?!!!!!!!!

yanying76

以下是引用kingsoft在2004-9-21 23:30:00的发言：

       选C

       原文说高盐浓度导致抗体失效

       选项说正常盐浓度抗体有用

       支持

但是泡在溶液里的人体组织不能说明问题，不是大活人一个

我觉得a更好

micht

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.

(A) indicates that after antibiotoic interacts with the highly salt concentration of fluid on the airyway, salt concentration returns to normal.

所以 effective antibotic 可以 cause salt concentraton return to normal! ==> 所以salt concentration不會導致ineffective antiboitc...無法strengthen hypothesis.. A不選

I'll choose C instead...is C correct?

starfishz

這題....是OG的吧???      我贊成C     

sarah81

Agree C.

calla

这题我也是选C, 但是我想问，B为什么不对？

supernova_zou

我认为b错在

1,b选项说A sample of the antibiotic 并不一定就是指的文中的antibiotic.

2,况且这个 antibiotic 在 high salt concentration 中也可以是有效的.