[求助]gwd-13-32

Seven9208

Q32:

Macrophages are cells that play a role in the response of the immune system of mice and other mammals to invasive organisms such as bacteria.  Unlike other mice, mice that are genetically incapable of making these particular cells do not show elevated levels of nitrates when infected with bacteria

The statements above, if true, provide the most support for which of the following conclusions?

• Mice that are unable either to make macrophages or to make them in sufficient numbers will protect themselves from bacterial infections in some other way.
  
• Mice that show elevated levels of nitrates can easily fight off most types of bacterial infections.
  
• In mice, macrophages play a role in the production of nitrates or inhibit a process by which nitrates are broken down or otherwise eliminated.
  
• When a healthy mouse becomes infected with an invasive organism, the number of macrophages in the mouse’s body decreases.
  
• Injections of nitrates into mice that lack macrophages will not enhance the ability of these animals’ immune systems to fight off infection.

   Answer:
C, 我选了a , 这个题我看了好几回,对题目的意思很迷糊,看了一下gwd讨论稿 一只大牛的分析,仍然看不懂c与题目的关系,还是很迷惑.  pls
help, thanks

lavenderwu

"Unlike other mice, mice that are genetically incapable of making macrophages do not show elevated levels of nitrates when infected with bacteria." means:

Normal mice: infected with bacteria --> making macrophages --> elevated levels of nitrates

Mice incapable of making macrophages: infected with bacteria --> no making of macrophages -> no elevated levels of nitrates

You can see that macrophages and level of nitrates are positively correlated.  Therefore, C can be reasonable inferred.

Seven9208

Thank you, it really make sense.

wyw1018

C:
In mice, macrophages play a role in the production of nitrates or inhibit a process by which nitrates are broken down orotherwise eliminated.

how to understand "otherwise eliminated" ?

thanks

faring56

B为什么不对呢？

这是归纳题题型，从这句话
Unlike other mice, mice that are genetically incapable of making these particular cells do not show elevated levels of nitrates when infected with bacteria，我推出了正常的mice， mice that are genetically capable of making these particular cells do show elevated levels of nitrates when infected with bacteria。再根据Macrophages are cells that play a role in the response of the immune system of mice and other mammals to invasive organisms such as bacteria. 选择了B。

我错在什么地方呢？望指正。谢谢！

krusher

B错的原因：有能力产Macrophage的mice在infected with bacteria 的时候能保持elevated level of nitrate，反之无能力产该“M”cell 的mice 在infected with bateria 的时候就不能有elevated level of nitrate。这是故事的梗概了。但由此并不能得出elevated level of nitrate 是用来fight with bacterial inflection的。也就是说他们两者的因果关系不是由nitrate到inflection 而应该是在inflection的情况下，看是否有能力产M，来决定nitrate的高低

ballackahn

B错的原因：有能力产Macrophage的mice在infected with bacteria 的时候能保持elevated level of nitrate，反 ...
krusher 发表于 2013-2-28 06:46

同意楼上


AB都有过度推导的嫌疑
文章只停留在产生nitrate的层面 并没有后续动作

ballackahn

C.    In mice, macrophages play a role in the production of nitrates or inhibit a process by which nitrates are broken down or otherwise eliminated.
清楚地表述了M和N的关系
文中说 有M的老鼠 N含量高 无M的老鼠 N含量低 （关心的是M和N的关系 并没有说能杀死细菌）
由此可见M对N有正面作用
所以M要么就是可以产生N  要么就是可以防止N消失