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?
A 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.
B Mice that show elevated levels of nitrates can easily fight off most types of bacterial infections.
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.
D When a healthy mouse becomes infected with an invasive organism, the number of macrophages in the mouse’s body decreases.
E Injections of nitrates into mice that lack macrophages will not enhance the ability of these animals’ immune systems to fight off infection.
"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.作者: citidandan 时间: 2010-10-25 21:06
Thank you, it really make sense@作者: parispings 时间: 2010-10-26 06:39
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.
how to understand "otherwise eliminated" ?
thanks
作者: WesternCder 时间: 2010-10-27 06:39
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。
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
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