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.

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 .



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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.

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.

But doesn't B contradict with the premise?

The premise suggests that after giving Naltrexone along with morphine, there were much fewer incidences of blood poisoning but still some.

If Naltrexone inhibits bacteria from migrating to the blood stream, then blood poisoning should have been completely eliminated.

Hence, I followed the logic that there must be other conditions, which cause blood poisoning, that Naltrexone eliminates, thus lowering the number of incidences of blood poisoning but not fully eliminating because morphine still causes blood poisoning in other cases where bacteria is induced to enter the blood stream.
In this case then, Naltrexone is not lowering the rates of blood poisoning through killing bacteria but dealing with other other conditions. --> weaken the argument.
Answer: E

Can someone help countering my logic?

@vertiaskarishma AjiteshArun
I rejected B because if Naltrexone inhibits morphine from triggering the migration of intestinal bacteria into the bloodstream. How does it explain there is still blood poising there should have been no blood poising ?
Wouldn't it be extreme to consider that there are other ways to have blood poising because the passage doesn't say anything about that

Researchers predict that Naltrex will turn out to be toxic to certain types of bacteria.

This is based on a study in which mice were given both morphine and Naltrex and researchers observed fewer blood poisonings.
We know that blood poisoning occurs when morphine is triggers intestinal bacteria to migrate into the bloodstream.

We are asked to weaken the support for the prediction (the premises perhaps) - we need to show that Naltrex MAY NOT necessarily be toxic to certain types of bacteria.

A is incorrect - we know Naltrex inhibits bacteria in some way shape or form in the bloodstream, so i'm not sure why Naltrex would need to pass into the intestine. It may be that Naltrex kills bacteria in the bloodstream only.

B is correct because it just tells us that Naltrex inhibits the bacteria from migrating, so researchers made an incorrect deduction. Naltrex does not kill the bacteria, it just inhibits it's movement. So in those few cases in which even after Rats were given Naltrex they were still poisoned, that's likely because the bacteria still migrated, and not because Naltrex didn't kill the bacteria because B tells us that 'killing' the bacteria isn't Naltrex's function.

C just tells us that Naltrex isn't poisonous or it won't cause greater risk of blood poisoning on its own, so I'm not sure how this would weaken the prediction.

D is incorrect - we are only concerned with Naltrex's impact in relation to blood poisoning

E is incorrect - it isn't conducive to the impact of Naltrex.
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(A) After being administered to mice, naltrexone does not pass from the bloodstream into the intestine. - Wrong: No Tie to Conclusion

(B) Naltrexone inhibits morphine from triggering the migration of intestinal bacteria into the bloodstream. - Correct: Alternate Explanation

(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. - Wrong: No Tie to Conclusion. Talks about "blood poisoning" and not "killing bacteria".

(D) The increased risk of blood poisoning is not the only harmful effect on mice of being given morphine. - Wrong: No Tie to Conclusion

(E) Conditions other than the presence of intestinal bacteria in the bloodstream can cause blood poisoning in mice. - Wrong: No Tie to Conclusion