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.

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Mice that have been given morphine are very likely to

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KarishmaB

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15 Jul 2025, 00:09

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When we claim "A must have caused B," then one way to weaken it is by claiming that "C could have caused B."

Here support for the researcher's claim is "N taken with Morphine reduces blood poisoning incidents" which as per author implies that N kills the bacteria.
But if we provide an alternative cause for reduction in blood poisoning (N inhibits morphine from triggering migration), then the claim that 'N kills the bacteria' loses its support. Note that it is still possible that N kills the bacteria but we are to raise doubts on the claim - not try to prove that it must be false.

Natansha

Hi KarishmaB I am confused between B & C. While I do understand why C can be wrong, we are not sure if N could still be toxic to some bacteria or not, the same goes for B option as well, ''Naltrexone inhibits morphine from triggering the migration of intestinal bacteria into the bloodstream'' even if it's true there could be a possibility that N kills the bacteria in the gut itself while inhibiting morphine or is still toxic to the bacteria in some way. I don't understand how it is right.

KarishmaB

Quote:

Morphine leads to blood poisoning in Mice because it makes bacteria migrate from intestine into the bloodstream.
Morphine with naltrexone leads to blood poisoning much less frequently.

Conclusion:
Naltrexone is will kill some types of bacteria.

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.

So this says that naltrexone does not cause blood poisoning i.e. it doesn't make bacteria migrate form intestine to bloodstream. It does not weaken that it kills some bacteria.

Hello KarishmaB and other EXPERTS

Can't we weaken the conclusion by establishing - Naltrexone ~~will kill some~~ will not kill any type of bacteria?
If so, C says that Naltrexone has no effect of its own and hence should be correct, right?

Please let me know where am I going wrong.

NischalSR

Conclusion:
Naltrexone will kill some types of bacteria.

(C) talks about giving N alone. It says that N does not increase the risk of developing blood poisoning. (They may have the same risk as without N or they may even have lower risk, we don't know. What we do know is that they do not have a greater risk of developing blood poisoning.)

Does it weaken that N is toxic to some bacteria? No. N could be toxic to some bacteria (lowering the risk of blood poisoning) or it may have no impact (the risk stays the same) on bacteria, we can't say. All we can say is that it doesn't increase the risk so it doesn't cause blood poisoning.
Hence (C) does not weaken our conclusion.