问gwd29-40

reginaer

我想请Ｎ们帮我分析以下这题：

 

Q40:

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, would most seriously weaken the support for the researchers’ prediction?

 

1. After being administered to mice, naltrexone does not pass from the bloodstream into the intestine.
2. Naltrexone inhibits morphine from triggering the migration of intestinal bacteria into the bloodstream.
3. Mice that have been given naltrexone but not morphine have no greater risk of developing blood poisoning than do mice that have not been given either substance.
4. The increased risk of blood poisoning is not the only harmful effect on mice of being given morphine.
5. Conditions other than the presence of intestinal bacteria in the bloodstream can cause blood poisoning in mice.

   Answer: Ｅ　　ＷＨＹ？

oumengling

My version says B is the answer. Here is my analysis:

The situation:

1. Morphine è bacteria migrate to blood stream è blood poisoning
2. Morohine + naltrexine è less frequent blood poisoning

è Prediction: Naltrexone is toxic to some bacteria

To weaken the SUPPORT of the prediction (i.e. weaken (2)), we must show that the less frequent blood poisoning is not because naltrexone kills bacteria, but rather did something else. (such that the evidence can no longer be used as support for the prediction.)

1. even if naltrexone does not get into intestine, it can still kill bacteria in the blood stream, after the bacteria are triggered by morphine to migrate to the blood stream.
2. Correct. This statement shows that naltrexone inhibits bacteria from causing blood poisoning by preventing them from migrating into the blood stream, a step earlier than that the researcher predicted. Therefore, the observed less frequent blood poisoning cannot support the prediction.
3. Mice that receive only naltrexone and those that receive none of the drugs are similarly unlikely to get blood poisoning. Because neither group of mice receive morphine, whether naltrexone kills bacteria is not important.
4. It may be true that morphine can cause additional side effects on mice. But it is only the bllod poisoning that we are interested in here. This statement is irrelevant.

oumengling

M会导致B进入血管，从而血液中毒；但是当M+N时，血液中毒少啦。推出N会导致B减少进入血管

Weaken support:N阻碍M去引起B进入血管