一道GWD的题目，死活想不通

mhm1616

Mice that have been given morphine are very likely to develop blood poisoning because bacteria that normally reside in the intestine typically respond to morphine by migrating into the bloodstream.  However, when mice are given both morphine and the new drug naltrexone, blood poisoning is much less frequent, although it does still occur.  These results provide support for researchers' prediction that naltrexone will turn out to be toxic to certain types of bacteria.

Which of the following, if discovered to be true, wouldmost seriously weaken the support for the researchers' prediction?

·    A After being administered to mice, naltrexone does notpass from the bloodstream into the intestine. 分析该选项

·    B Naltrexone inhibits morphine from triggering themigration of intestinal bacteria into the bloodstream. 分析该选项

·    C Mice that have been given naltrexone but not morphinehave no greater risk of developing blood poisoning than do mice that have notbeen given either substance. 分析该选项

·    D The increased risk of blood poisoning is not the onlyharmful effect on mice of being given morphine. 分析该选项

·    E Conditions other than the presence of intestinal bacteriain the bloodstream can cause blood poisoning in mice. 分析该选项

正确答案 B，我怎么一直觉得B是加强，不是削弱

Trey_

再看一下那个prediction：nal能够减少blood poisoning的原理是它能够毒死那种细菌。
而B选项对nal的作用机理提出了另一种解释：nal没有毒死细菌，他只是防止了细菌移动到血液里。
如果B这种作用机理成立，那么prediction的作用机理就不对了。

总之，问题就在于这道题需要你去削弱什么。你需要削弱的不是“nal有用”这一点，而是“nal的作用机理是毒死细菌”这一点。
祝好~