Using new detection techniques, researchers have found trace amounts

wil go with E. looks to be the best possible answer
as low concentration can make the bacteria resistant and hence when humans are infected by these bacteria treating humans will pose a problem.

(A) some of the medicinal substances found in lakes and rivers are harmless to humans in large quantities shifts the focus to large quantities. We need to focus on small quantities and their removal
(B) some of the medicinal substances found in lakes and rivers can counteract possible harmful effects of other such substances found thereweakens the contention of medical experts
(C) people who develop undesirable side effects when being treated with medicines that contain these substances generally have their treatment changedout of scope
(D) most medicinal substances that reach lakes or rivers rapidly break down into harmless substancesweakens the contention of medical experts
(E) disease-causing bacteria exposed to low concentrations of certain medicinal substances can become resistant to themCORRECT - provides the correct focus and contention


What's the OA?

Answer should be E. Reasoning in red.

Which of the following most logically completes the passage?

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
Weakens the claim
(B) some of the medicinal substances found in lakes and rivers can counteract possible harmful effects of other such substances found there
It weakens the experts' claim
(C) people who develop undesirable side effects when being treated with medicines that contain these substances generally have their treatment changed
Treatment has nothing to do with the amounts found in water
(D) most medicinal substances that reach lakes or rivers rapidly break down into harmless substances
Weakens the claim
(E) disease-causing bacteria exposed to low concentrations of certain medicinal substances can become resistant to them
Can be the answer as it supports the claim and gives valid reason to itplease, provide your reasoning along with answers

+1 for E.

This is a classical Explain the Situation/paradox problem. The first step for such problems is to identify the paradox:

Premise: Harmful substances are present in quantities far too low to cause any health problems.
General Conclusion: Generally this means that medical experts would consider that eliminating these substances will have NO benefits.
Paradox/Situation: Medical experts consider that eliminating these substances WILL have health benefits.

To explain the situation, we need an answer choice which explains why general conclusion does not happen(or is not true) and paradox happens(or is true).

E explains just that by implying that harmful sustances have health implications, even if they are present in small quantities.

Crick

You've got it the other way round. You must choose the option that helps to establish that eliminating these substances from the water WILL have health benefits.

(B) provides an argument to let the substances stay, i.e. not remove them. Exactly the opposite of what we are looking for. Irrelevant.
(E) provides a clear explanation for why removing these substances will have health benefits.

Therefore (E) is correct.

The argument only speaks about the effects of the medicine present in the water. Option C speaks about the medicines used when treating patients. Hence it is completely out of scope. It only creates an illusion of staying close to the argument by using similar words.

E speaks directly about low concentrations of the medicine. The argument says that the medicine found in the water supply is of low concentration. So E stays close to the argument. Hence E is the right answer.


Kudos Please... If my post helped.

(A) some of the medicinal substances found in lakes and rivers are harmless to humans in large quantities

Wrong, because it just repeats a premise and doesn't help the conclusion.

(B) some of the medicinal substances found in lakes and rivers can counteract possible harmful effects of other such substances found there

Wrong, because it weakens the conclusion. We need an answer that says removal of these substances can benefit people.

(C) people who develop undesirable side effects when being treated with medicines that contain these substances generally have their treatment changed

Wrong, because it is out of scope. People who are treated with these meds are not the focus of the argument.


(D) most medicinal substances that reach lakes or rivers rapidly break down into harmless substances

Wrong, because it weakens the conclusion. Same reason as A.


(E) disease-causing bacteria exposed to low concentrations of certain medicinal substances can become resistant to them

Correct, because it supports the fact that removal of these substances will benefit the public.

Conclusion: eliminating these trace amounts from the water will have public health benefits
Answer choice : Should strengthen the conclusion

A. Some of the medicinal substances found in lakes and rivers are harmless to humans in large quantities.
Not related. On the contrary this negates the premise stated in the argument.
B. Some of the medicinal substances found in lakes and rivers can counteract possible harmful effects of other such substances found there.
This says that having these substances is beneficial because they counteract possible harmful effects of other substances.
Leaving out these substances actually weakens the conclusion (since conclusion is to eliminate these trace amounts)
C. People who develop undesirable side effects when being treated with medicines that contain these substances generally have their treatment changed
We can say that this is already known from the argument since large quantities pose serious health effects. This choice continues further to say that if medicines have large amount then the treatment needs to be changed as they post serious health effects
D. Most medicinal substances that reach lakes or rivers rapidly break down into harmless substances
This also weakens the conclusion, because, if the trace amounts breakdown and become harmless, then there is no need to eliminate
E. Disease-causing bacteria exposed to low concentrations of certain medicinal substances can become resistant to them.
If disease causing bacteria becomes resistant, then there will be health risks to the public. This is because at the moment these trace amounts are killing the bacteria and hence are not a problem now. If not eliminated, might make the bacteria resistant resulting in health issues. Hence strengthens the conclusion.

Thanks

Could someone explain why B is incorrect?

Hi there,
if you break out the conclusion, you will probably find this sentence rather easy.
The conclusion states that there would be benefits in eliminating the trace amount of medicinal substances from lakes and rivers.

Option B states that the medicinal substances can counteract possible harmful effects of substances found there. Clearly, it would not be beneficial to remove something that is good for the lakes and rivers. Therefore, this answer choice is paradoxical and rather states the opposite of what should be stated.

Instead, take a look at answer choice E. This option states a disadvantage of not eliminating the medicinal substances - that the bacteria in the river may become resistant. Hence, this is the right answer choice.

E states that the bacteria will become resistant to the traces and therefore removing the traces will have health benefits since the bacteria will then not be resistant (to the medicinal traces). However, that does not mean that the bacteria will cease to exist (which is what should be the case to classify it as a health benefit). The bacteria exists with or without the traces. Can somebody please clarify this confusion?

Which of the following most logically completes the passage?

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 ____________.

Medicinal Substances - found in lake and river.
They are present is small quantities, hence low physiological response.
But still, medical experts are eliminating these traces because it will improve the public health benefits. Why?

(A) some of the medicinal substances found in lakes and rivers are harmless to humans in large quantities
Wrong. Weaken's the conclusion. If the medicinal substance are harmless to humans in large quantities then why are they eliminating it?

(B) some of the medicinal substances found in lakes and rivers can counteract possible harmful effects of other such substances found there
Wrong. It weakens the conclusion. If these medical substances can stop other possible harmful effects of other such substance, then why is government removing it?

(C) people who develop undesirable side effects when being treated with medicines that contain these substances generally have their treatment changed
Wrong. The medicines that contain these substances are extremely high potent and thus has side effects. But in the rivers they are in very less quantity.

(D) most medicinal substances that reach lakes or rivers rapidly break down into harmless substances.
Wrong. If the medicinal substances break into harmless substances, then why is government trying to remove these substances?

(E) disease-causing bacteria exposed to low concentrations of certain medicinal substances can become resistant to them
Right. If the diseases causing bacteria become resistant to these medical substances, then that means nothing else can stop those bacteria from spreading the diseases. And that is why government is removing them.

Which of the following most logically completes the passage?

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 ____________.

Conclusion: "eliminating these trace amounts from the water will have public health benefits" --> we want to prove these substances are bad for health

(A) some of the medicinal substances found in lakes and rivers are harmless to humans in large quantities

remember we are proving that these substances are bad for health. What A is saying is that these substances are harmless --> not bad for health, even in large quantities. In addition, from the premise, we know that large quantities will harm health. Choice A contradicts the premise. Therefore, wrong.

(B) some of the medicinal substances found in lakes and rivers can counteract possible harmful effects of other such substances found there

counteract definition: if you counteract something, you do the reduce its effect and produce a opposite effect.
In B, these medical substances counteract (reduce) the harmful effects. However, we are looking for something bad about these substances. Therefore, wrong.

(C) people who develop undesirable side effects when being treated with medicines that contain these substances generally have their treatment changed

So first, our goal is to prove that it is beneficial to eliminate substances in the river. Therefore, whatever amount of substances you put in medicine taken by patients that might have big/huge/immense/small/little or whatever effects, we know, from the premise, the river contains little and doesn't have any harmful effects. Therefore, this answer choice is actually contradicting the premise or you can say it is irrelevant.
In addition, the people in choice C have had their treatment changed. In that case, there is nothing to worry about any harmful effects of the medicine. You can try to put this sentence in the line and read it with the last sentence, you will find that "have their treatment changed" just won't make sense because this phrase plays as a main verb in this clause and this phrase doesn't only helps to explain these substances do no bad things.

(D) most medicinal substances that reach lakes or rivers rapidly break down into harmless substances

This choice only explains that substances are harmless. But we want to prove substances are bad. Therefore, wrong.

(E) disease-causing bacteria exposed to low concentrations of certain medicinal substances can become resistant to them

"disease-causing bacteria" --> say virus. "resistant" --> in medical terms, when A is resistant to B, it means that B has no effects on A
First we know medicines helps people to kill bad bacteria/virus/help recover. Choice E is saying that if we do not eliminate these medical substances, these substances will have no effects on the virus or could not kill/harm virus --> not eliminating the substances will affect its effectiveness in killing the virus --> bad for ppl. Therefore, this is the answer we are looking for.

VeritasKarishma : Follow up on E

The OA solution for CR problems should not have to make a "hopeful assumption" per my understanding.

Doesn't E E make a hopeful assumption ?


The hopeful assumption is that the certain medicinal substances in E are the same medicinal substances discussed in the stimulus

Isn't that technically an hopeful assumption ?

If the medicinal substances are not the same, It's quite possible that the properties of the medicinal substances discussed in E don't necessarily apply to the medicinal substances discussed in the stimulus

Just wondering, how far should one take this concept of hopeful suggestion .

- Researchers have found trace amounts of various medicinal substances in lakes and rivers.
- Concentration is far too low to cause any physiological response (any harm) in people who drink the water or bathe in it.

Conclusion: Nevertheless, medical experts contend that eliminating these trace amounts from the water will have public health benefits,

since ....

Though the concentration of various medicinal substances found is very low, still experts contend that we should eliminate them for public health since ...
Whatever completes the sentence will tell us why even low concentrations of medicinal substances could be harmful to public health and hence should be eliminated.

(A) some of the medicinal substances found in lakes and rivers are harmless to humans in large quantities

Incorrect. Doesn't tell us why low concentrations could be harmful.

(B) some of the medicinal substances found in lakes and rivers can counteract possible harmful effects of other such substances found there

Incorrect. Doesn't tell us why low concentrations could be harmful.

(C) people who develop undesirable side effects when being treated with medicines that contain these substances generally have their treatment changed

Side effects of these medicine during treatment is irrelevant. We are discussing why trace amounts of these medicines should be removed from lakes and rivers water.

(D) most medicinal substances that reach lakes or rivers rapidly break down into harmless substances

Incorrect. Doesn't tell us why low concentrations could be harmful.

(E) disease-causing bacteria exposed to low concentrations of certain medicinal substances can become resistant to them

Correct. It tells us that bacteria that cause diseases can become resistant to medicines if exposed to their low concentrations. So eventually this could impact human health because these bacteria could cause diseases in humans and be immune to medicines.
Hence, this is a valid reason to eliminate these medical substances from lakes and rivers.

The argument tells us that there are "various medical substances" found. It means a large variety of medical substances were found. Bacteria could become resistant to some of them. It's perfectly valid to think that "certain medicinal substances" will have overlap on "various medicinal substances".

Answer (E)

jabhatta2:
I don't understand what you mean by hopeful assumption or suggestion. You are confusing yourself unnecessarily by getting into such terminology. Stick to the official terminology used in GMAT questions only and use simple logic to get your answers.
I do not understand

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