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?

(A) After being administered to mice, naltrexone does not pass from the bloodstream into the intestine.

(B) Naltrexone inhibits morphine from triggering the migration of intestinal bacteria into the bloodstream.

(C) 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.

(D) The increased risk of blood poisoning is not the only harmful effect on mice of being given morphine.

(E) Conditions other than the presence of intestinal bacteria in the bloodstream can cause blood poisoning in mice.

I think its B..

it says the nextrone doesnt kill any bectaria but stops morphine from doing what it previously did..

The conclusion from the statement is that: "results provide support for researchers’ prediction that naltrexone will turn out to be toxic
to certain types of bacteria."

We are looking for a statement that breaks the logic between naltrexone and bacteria.

B. does this by saying that naltrexone acts on the morphine, not the Bacteria.
E. This MAY be true but it does not weaken the conclusion.

OA???

C.
the conclusion is about nextrolene being toxic to bacteria ...
(C)suggests that nextrolene will have no effect whatsoever on mice, so it weakens the argument that nextrolene can be toxic to certain types of bacteria...

has to be B.

bacteria that normally reside in the intestine typically respond to morphine by migrating
into the bloodstream and cause blood poisoning. C is that N will be toxic to certain bacteria

Weaken

Look for choice that says N will NOT be toxic to intestinal bacteria. If N were to suppress the B-M interaction, blood poisoning would not occur and it cannot turn out to be toxic.

E says that some thing else causes BP. the conclusion here is more weakened by B by saying that N will not turn out to be toxic afterall.

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?

The prediction is that naltrexone is toxic to bacteria since mice given morphine with naltrexone don't develop blood poisoning, normally caused by the intestine's response to morphine. To weaken this prediction one needs to find a different mechanism for naltrexone.
A. After being administered to mice, naltrexone does not pass from the bloodstream
into the intestine. Where naltrexone passes isn't relevant.
B. Naltrexone inhibits morphine from triggering the migration of intestinal bacteria
into the bloodstream.
C. 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. We already know that morphine induces blood poisoning. What occurs in the absence of morphine isn't relevant.
D. The increased risk of blood poisoning is not the only harmful effect on mice of
being given morphine. Anything other than blood poisoning is out of scope
E. Conditions other than the presence of intestinal bacteria in the bloodstream can
cause blood poisoning in mice. Other causes of blood poisoning are out of scope.

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?

A. After being administered to mice, naltrexone does not pass from the bloodstream into the intestine.
That means morphine released the bacteria into blood stream and the N acted on that bacteria .
Strengthen

B. Naltrexone inhibits morphine from triggering the migration of intestinal bacteria into the bloodstream.
N acts on M, not the bacteria .
Weakens

C. 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.
Talks about blood poisioning rather than N action on bacteria.
Irrilevent
D. The increased risk of blood poisoning is not the only harmful effect on mice of being given morphine. Talks about harmful effects of blood poisoning.
Irrilevent

E. Conditions other than the presence of intestinal bacteria in the bloodstream can cause blood poisoning in mice. Oos / opposite answer

Talks about conditions other than bacteria itself . That means it doesn't matter whether N acts on bacteria , blood poisoning occurs from other means .



Sent from my Le X507 using GMAT Club Forum mobile app
_________________

without a doubt it's B.
B says that new drug "destroys" morphine...definitely a weakener!
_________________

Explanation:

The argument states that naltrexone is harmful for many strains of bacteria. The evidence to support this conclusion is that when mice were given this new drug along with morphine, they had fewer cases of blood poisoning than they did in situations where the mice were given only morphine, which triggered harmful intestinal bacteria to mix with the blood of the mice. We need to prove that despite the reduction in the incidences of blood poisoning after the administration of the drug, the new drug has not damaging effect on the harmful bacteria.

Whether the new drug moves or not is irrelevant in knowing its effect on the bacteria.
CORRECT. As per this option, the new drug does not kill harmful bacteria. Rather, it only hampers the movement of these bacteria to the blood of the mice. Thus, whereas this new drug can be said to be good for the mice, since it prevents the cases of blood poisoning, it does not have a direct damaging effect on the harmful bacteria itself. This helps weaken the conclusion.
Mice which are given only the new drugs have the same chances of being bold poisoned. This will only prove the negative effect of the new drug on the mice. But this still does not clarify the relation between the new drug and the harmful bacteria.
We are not probing into the number of harmful effects of morphine.
‘Other causes of blood poisoning’ is again out of scope.

In addition to "stop", apparently "inhibit" can also mean "hinder/resist".

So, that resistance/hindrance might not ultimately result in 100% success (in preventing migration of intestinal bacteria into the bloodstream).