Using new detection techniques, researchers have found trace

[tusharkhatri18]

Using new detection techniques, researchers have found trace amounts of various medicinal substances in lakes and rivers. Taken in large quantities, these substances could have serious health effects, but they are present in quantities far too low to cause any physiological response in people who drink the water or bathe in it. Nevertheless, medical experts contend that eliminating these trace amounts from the water will have public health benefits, since ____________.

A. Some of the medicinal substances found in lakes and rivers are harmless to humans in large quantities.
B. Some of the medicinal substances found in lakes and rivers can counteract possible harmful effects of other such substances found there.
C. People who develop undesirable side effects when being treated with medicines that contain these substances generally have their treatment changed
D. Most medicinal substances that reach lakes or rivers rapidly break down into harmless substances
E. Disease-causing bacteria exposed to low concentrations of certain medicinal substances can become resistant to them.

Please tell why option D is wrong and how is option E correct?
Also, please tell how to find the type (weaken, strengthen or assumption) of Argument Completion. Is it necessary to find out ever?

[RonPurewal]

If eliminating the substances from the water will bring benefits, then the substances must have some BAD effect on health.

So, you need to find what that bad effect is.

D. Most medicinal substances that reach lakes or rivers rapidly break down into harmless substances

"Harmless". I.e., NOT bad. They have no ill effect.

This is the opposite of what you want. If this statement is true, then removing the substances from the water will have no effect at all.

E. Disease-causing bacteria exposed to low concentrations of certain medicinal substances can become resistant to them.

This is very bad!
This means that, if you leave the substances in the water, they won't kill these bacteria anymore!

If this is true, then removing the substances from the water will allow the medicines to continue working"”clearly a health benefit.

[RonPurewal]

Also, please tell how to find the type (weaken, strengthen or assumption) of Argument Completion. Is it necessary to find out ever?

"Fill in the blank" problems can be absolutely any type of CR task at all.

* If you can read the passage and intuitively understand what kind of thing has to go in the blank, then there's no need to classify anything. (This is true for CR in general; if you already understand a task intuitively, then classifying stuff is at best unproductive, and at worst counterproductive.)

* If you're having trouble, then you should look for signs that indicate what kind of task you're doing. Here, you have "since", so you need a reason for what the experts believe. This is equivalent to strengthening their argument.

[tusharkhatri18]

If this is true, then removing the substances from the water will allow the medicines to continue working"”clearly a health benefit.

Hi Ron,
Thanks for the explanation. But I got a doubt here.

If we are removing substances from the water, then from where medicines came? I think you are referring medicines to medicinal substances. They are same. So, according to me, the medicines can't work if substances are removed.
Kindly explain in detail if I am wrong.

[RonPurewal]

If this is true, then removing the substances from the water will allow the medicines to continue working"”clearly a health benefit.

Hi Ron,
Thanks for the explanation. But I got a doubt here.

If we are removing substances from the water, then from where medicines came? I think you are referring medicines to medicinal substances. They are same. So, according to me, the medicines can't work if substances are removed.
Kindly explain in detail if I am wrong.

I'm not following you here.

Replace "medicines / medicinal substances" (yes, those are the same) with, say, "antibiotics".

* There are trace amounts of antibiotics in the water.

* The amounts are too small to affect humans.

* However, because germs in the water are exposed to them, they may unintentionally create antibiotic-resistant strains of those germs.

* If we filter them from the water, then we won't produce those super-germs.
Better result for people.

Please let me know which part of the above you don't understand. Thanks.

[tusharkhatri18]

Hi Ron,
Now it is clear to me. Thanks for the explanation.
It was one of the question where I was thinking every answer choice to be wrong. Can you tell me what is the level of this question? 700-800 level? Is it a hard one?

[RonPurewal]

Hi Ron,
Now it is clear to me. Thanks for the explanation.
It was one of the question where I was thinking every answer choice to be wrong. Can you tell me what is the level of this question? 700-800 level? Is it a hard one?

To a test taker, difficulty levels are a complete unknown. (By asking this question, you've proved this point yourself!) Therefore, there is no sense in thinking about them.

You should treat every problem just as seriously as every other problem.

[sri balaji143]

Ron,

Could you please explain why C is wrong. I narrowed it down to C and E. E clicked but I didnt have any point to eliminate C. Is C wrong because some people have their treatment changed. That is just a small exception to the trend or is it wrong for a different reason. Im not able to make an anology either.

Thanks in advance,
B

[RonPurewal]

the passage tells us that these drugs are "present in quantities far too low to cause any physiological response in people".

in other words, the drug substances in the water CANNOT AFFECT PEOPLE DIRECTLY. that's a FACT.

thus, any effect of these substances ON PEOPLE is irrelevant here.

[MdAbuAsad]

the passage tells us that these drugs are "present in quantities far too low to cause any physiological response in people".

in other words, the drug substances in the water CANNOT AFFECT PEOPLE DIRECTLY. that's a FACT.

thus, any effect of these substances ON PEOPLE is irrelevant here.

I think, the red part is applicable to only those people ( not all the peoples in this planet) who drink the water or bathe in lakes and rivers. Am I right expert?
Thanks...

[Sage Pearce-Higgins]

Yes, I think Ron was a little rash in his phrasing. He's just saying that these substances have no direct influence on people who drink the water or bathe in it. This can help us eliminate answer C. Clearly the right answer (E) shows that these substances can cause indirect negative effects.

[MdAbuAsad]

I thought so-he was rash in this choice (C). Ron was my online course tutor when he was an instructor of ManhattanPrep. I know the power of Ron-he can't be wrong anymore! If he does any mistake in the explanation of any question of GMAT, it is totally unintentional!
I'm not here to find the fault of Ron; I'm here to test the CR level of mine.
Thanks Sage Pearce-Higgins___

[Sage Pearce-Higgins]

You're welcome.

[JbhB682]

Hi Sage -- a followup on the OA E.

Link : https://www.manhattanprep.com/gmat/forums/explain-the-apparently-surprising-result-gprep1-t6676.html#p65690

In above Manhattan forum link , I read about the importance of not making 'hopeful assumptions' about answer choices.

In other words, one cannot hypothesize random possibilities about the answer choices and then argue from those possibilities.

I thought E forces us to make a hopeful assumption.

E mentions certain medicinal substances -- how we can confirm if these are the SAME medicinal substances being discussed in the stimulus ?

It's very well possible that the bacteria become anti-resistant to the medicinal substances (That were mentioned in E) but not anti-resistant to other medicinal substances (that the stimulus were referring too). There is no proof the suggest that medicinal substances mentioned in E are the exact same medicinal substances mentioned in the stimulus.

Is it not an an example of a hopeful assumption we are making that the medicinal substances are the same ?

Thank you for everything !

[Sage Pearce-Higgins]

You're right - we can't be sure that the substances are the same. I would encourage you to keep in mind a couple of things. First, remember that we're looking for an answer that strengthens the conclusion. This is not the same as proving the conclusion with 100% certainty. Answer E raises the possibility that these substances could have a harmful effect on human health. Second, although I agree that hopeful assumptions are to be avoided, we need to be reasonable when understanding Critical Reasoning problems. Sure, there may be a fine line between being reasonable and making assumptions. After all, all understanding of language is based on some knowledge of the real world, but, in my experience, GMAT treads that fine line pretty carefully. What helps me out on a problem like this one is a bit of background knowledge: antibiotic resistance due to discarded medicines is a real phenomenon.