Researchers in City X recently discovered low levels of several pharma

Question

Researchers in City X recently discovered low levels of several pharmaceutical drugs in public drinking water supplies. However, the researchers argued that the drugs in the water were not a significant public health hazard. They pointed out that the drug levels were so low that they could only be detected with the most recent technology, which suggested that the drugs may have already been present in the drinking water for decades, even though they have never had any discernible health effects.

Which of the following, if true, would most strengthen the researchers' reasoning?

A. If a drug found in drinking water is not a significant public health hazard, then its presence in the water will not have any discernible health effects.

Which of the following, if true, would most strengthen the researchers' reasoning?

A. If a drug found in drinking water is not a significant public health hazard, then its presence in the water will not have any discernible health effects.

B. There is no need to remove low levels of pharmaceutical drugs from public drinking water unless they present a significant public health hazard.

C. Even if a substance in drinking water is a public health hazard, scientists may not have discerned which adverse health effects, if any, it has caused.

D. Researchers using older, less sensitive technology detected the same drugs several decades ago in the public drinking water of a neighboring town but could find no discernible health effects.

E. Samples of City X's drinking water taken decades ago were tested with today's most recent technology, and none of the pharmaceutical drugs were found.

CR61021.01

GMATIntensive · Accepted Answer

The Story     
 Researchers in City X recently discovered low levels of several pharmaceutical drugs in public drinking water supplies.  - Low levels of drugs were recently discovered in water supplies.

However, the researchers argued that the drugs in the water were not a significant public health hazard.  - ‘However’ signifies the author will present a contrast. The researchers claim that the drugs are not a significant health hazard. Why is the word ‘however’ used? To explain that although pharmaceutical drugs were found in water, the drugs are not a significant health hazard.

They pointed out that the drug levels were so low that they could only be detected with the most recent technology,  - only recent technology enabled them to discover the drugs.

which suggested that the drugs may have already been present in the drinking water for decades, even though they have never had any discernible health effects.  - The fact that the drugs could only be detected using the latest technology indicates that the drugs may have been present in the water for many years. Yet, there haven’t been any related health concerns in that time.

Gist:  Drugs have been found in water. Since the technology to detect is new,  the drugs may have been present in water for many years. Since there haven’t been any identifiable health effects ,    drugs in the water are not a significant health hazard (researchers’ conclusion).  .

The Gap

The argument is based on mere possibilities. Because we could not test for these levels of drugs in water earlier, drugs  may have been  present for decades. Well sure, drugs may have been present. But they very well may not have been present too. Just on the basis of this possibility the researchers build their argument and claim that the levels of drugs in water do not constitute a significant health hazard. What if the drug levels went up only recently?

Also, even if drugs have been present in water for decades, no ‘discernible health effects’ does not necessarily mean ‘no effects’. It just means effects were not identified.

There could, of course, be more gaps as well.

The Goal     
We need to strengthen our belief in the researchers’ argument that the drugs in the water are not a significant health hazard. Bridging one of the gaps could be a good way to strengthen.

The Evaluation     
 A. If a drug found in drinking water is not a significant public health hazard, then its presence in the water will not have any discernible health effects. 
  Incorrect  . We need to pay close attention here. We discussed above that no ‘discernible health effects’ does not necessarily mean no health effects. If we are not precise, this option seems to alleviate that concern. However, this option actually reverses the conditional. We are interested in figuring out: if a drug found in water is a health hazard, then will its presence in the water have any discernible health effects?

Basically, on the basis of ‘no discernible health effects’ is it safe to infer ‘no high levels of drugs in water’ and thus ‘not a significant health hazard’? That is how the argument is built. The argument assumes that ‘no discernible health effects’ is sufficient to conclude ‘no significant health hazards’.

What we are given here is: ‘not a significant health hazard’ implies ‘no discernible health effects’. This option changes the direction of the sufficiency. That does not help the argument.

Here’s an example to understand this further:
Argument: If a person does not have a blue eye, we can conclude that the person has not been in a fight. (relate this with the argument)

Statement: If a person has not been in a fight, the person cannot have a blue eye. (relate this with this option)

Does the above statement strengthen the above argument?

Nope. Just because ~X (no fight) means ~Y (no blue eye) doesn’t mean that ~Y means ~X. We can easily have ~Y (no blue eye) and X (a fight).A person could have been in a fight with someone much weaker and not got hurt at all. He could have been hurt in other ways. He could have very well still fought.

The same reasoning applies to this option as well.

How about this statement: If a drug found in drinking water is not a significant public health hazard, then its presence in the water will not have any discernible health effects.

What impact does this statement have on the argument?

B. There is no need to remove low levels of pharmaceutical drugs from public drinking water unless they present a significant public health hazard. 
  Incorrect  . Researchers’ argument is that the drugs in the water are not a significant health hazard. Whether we need to remove the drugs from water is beyond their argument.

C. Even if a substance in drinking water is a public health hazard, scientists may not have discerned which adverse health effects, if any, it has caused. 
  Incorrect  . Scientists may not have discerned ‘which’ adverse health effects a health hazard has caused. This is not the same as scientists may not have discerned ‘whether’ there were adverse health effects. Even if the scientists were not able to pinpoint which adverse health effect a substance caused they could have still understood ‘whether’ a substance had adverse health effects.

Let us also consider the statement we made above: Scientists may not have discerned (detected) whether there were adverse health effects. Does this statement strengthen the argument? It doesn’t. It actually weakens the argument. This is the second gap we have discussed above.

Researchers using older, less sensitive technology detected the same drugs several decades ago in the public drinking water of a neighboring town but could find no discernible health effects. 
  Correct  . So researchers did detect these drugs in the water in another town decades ago. And they could not find any visible side effects. Ok, so these drugs very well may be present in the water and yet there may not be any noticeable effects. That does increase our belief in the researchers’ reasoning. These drugs do not manifest any noticeable health effects, and likely are not a significant public health hazard.

Let’s look at one more aspect. How come researchers were able to detect the drugs ‘several decades ago’ when the passage states that ‘they could only be detected with the most recent technology’? The passage says that the levels were ‘so low’ that only the latest technology could detect the drugs. So, if in a neighboring town researchers could detect the drugs several decades ago with older, less sensitive technology, that indicates that the levels of drugs would have been higher. If even those higher levels did not lead to any discernible health effects, it is likely that even the current low levels would not and thus the drugs in the water are not a significant health hazard.

E. Samples of City X's drinking water taken decades ago were tested with today's most recent technology, and none of the pharmaceutical drugs were found. 
  Incorrect  . Wait a minute. Old samples did not have the drugs? That would likely mean that the reason there were no ‘discernible health effects’ is that there were no drugs in the water. The drugs perhaps only recently got added to the water. This option is clearly in the opposite direction, and weakens the argument.

Before we get too engrossed in the nitty-gritty, it helps to understand what ‘direction’ an option is taking our argument in. This one clearly is going in the opposite direction. It reduces our belief in the reasoning and is thus incorrect.

Additional Notes     
 SC Notes:

1. In the third statement of the passage, notice the use of ‘which’ to refer to the entire clause. 
2. Notice the three occurrences of ‘they’ in the third statement. 
They (researchers - mentioned in the previous sentence) pointed out that the drug levels were so low that they (drugs - mentioned in the previous sentence) could only be detected with the most recent technology, which suggested that the drugs may have already been present in the drinking water for decades, even though they (drugs) have never had any discernible health effects.

If you have any doubts regarding any part of this solution, please feel free to ask.

KarishmaB · Answer

Low levels of drugs found in water.
Drug levels were so low that they could only be detected with the most recent technology, 
so drugs may have already been present in the drinking water for decades, even though they have never had any discernible health effects.

Conclusion - Drugs in the water are not a significant public health hazard.

We need to strengthen the reasoning.

A. If a drug found in drinking water is not a significant public health hazard, then its presence in the water will not have any discernible health effects.

Incorrect. The reverse would have helped us - if there are no discernible health effects, then they will not be a public health hazard.
We know that there are no discernible health effects and based on that we are concluding that they are not a public health hazard. In "if A, then B", A implies B so it would have helped us.
As given, this if statement doesn't help us.

B. There is no need to remove low levels of pharmaceutical drugs from public drinking water unless they present a significant public health hazard.

Whether we need to remove them or not is not a point of discussion at all.

C. Even if a substance in drinking water is a public health hazard, scientists may not have discerned which adverse health effects, if any, it has caused.

This doesn't help our argument. We need to say that drugs are not a public health hazard. This says that we may not discern adverse health effects even if it is a public health hazard. So this opens the possibility that it could be a public health hazard. Against our conclusion.

D. Researchers using older, less sensitive technology detected the same drugs several decades ago in the public drinking water of a neighboring town but could find no discernible health effects.

This says that same drugs had no discernible health effects elsewhere too. So it strengthens the argument that the drugs are not public health hazard. Answer.

E. Samples of City X's drinking water taken decades ago were tested with today's most recent technology, and none of the pharmaceutical drugs were found.

Against our reasoning. We are saying that this level of drugs may have been present for a long time but there have been no discernible health effects. If decades ago, these drugs were not there in water, it is possible that the drugs in water are a recent addition and negative health effects are yet to show. So the drugs could be a public health hazard.

Answer (D)

Kanika3agg · Answer

Researchers in City X recently discovered low levels of several pharmaceutical drugs in public drinking water supplies. However, the researchers argued that the drugs in the water were not a significant public health hazard. They pointed out that the drug levels were so low that they could only be detected with the most recent technology, which suggested that the drugs may have already been present in the drinking water for decades, even though they have never had any discernible health effects.

Which of the following, if true, would most strengthen the researchers' reasoning?

A. If a drug found in drinking water is not a significant public health hazard, then its presence in the water will not have any discernible health effects.

Reasoning of the Scientists - The drugs would have already been present in the water for decades and they have never had any discernible health effects.

Which of the following, if true, would most strengthen the researchers' reasoning?

A. If a drug found in drinking water is not a significant public health hazard, then its presence in the water will not have any discernible health effects. -  This statement doesn't strengthen the point of scientists that the drugs were present for decades in the water.

B. There is no need to remove low levels of pharmaceutical drugs from public drinking water unless they present a significant public health hazard. -  Not related to reasoning. 
C. Even if a substance in drinking water is a public health hazard, scientists may not have discerned which adverse health effects, if any, it has caused. -  This weakens the reasoning.
 
D. Researchers using older, less sensitive technology detected the same drugs several decades ago in the public drinking water of a neighboring town but could find no discernible health effects. -  This is strengthening the reasoning clearly.

E. Samples of City X's drinking water taken decades ago were tested with today's most recent technology, and none of the pharmaceutical drugs were found. -  This weakens the reasoning

In all the Strengthen questions, if we can find what we have to strengthen, the answer finding becomes very easy.

gmatt1476 · Answer

Official Explanation

Argument Evaluation

This question asks us to find the answer choice that would most strengthen this argument.

Researchers in City X reason that because the levels of certain pharmaceutical drugs that have been found in the city's drinking water are so low—detectable only by use of the most recent technology—these drugs may well have been in the drinking water for decades. Furthermore, the researchers point out that there have been no discernible health effects from the use of the drugs. They conclude that the drugs are probably not a significant concern.

As it stands, the argument is quite weak. The researchers conclude only that the drugs may have . . . been present for decades. This leaves open the possibility that they were not present for that long. If they were not, then obviously the current lack of discernible health effects does not imply that there will be no such effects in the future.

We can strengthen the argument if we find solid information indicating that these drugs can be present in a city's drinking water at the levels found in City X's drinking water, or higher, for a long time without presenting any ill health effects.

A. This choice does not strengthen the argument. Note that there have not been any discernible health effects from drinking the water; this fact is compatible with this statement as well as with the drug being a significant public health hazard. Perhaps the reason there have been no discernible health effects is that the drugs have only recently entered the water supply.

B. This choice does not strengthen the argument's reasoning. Until we can establish that there is no significant health hazard—what the argument sets out to prove—we cannot know whether there is a need to remove these drugs from the drinking water.

C. This claim weakens the argument. It introduces the possibility that there may have been adverse health effects resulting from these drugs, yet the researchers have not been able to discern these effects, or have not been able to determine that they were effects of the drugs.

D. Correct. Researchers several decades ago, using less sensitive technology, were able to detect the same drugs in another town's public drinking water. This implies that the drug levels in that town were higher than those recently detected in City X's drinking water. Given that there have been no discernible health effects in this previous case, this lends support to the researchers' reasoning regarding City X.

E. This claim weakens the argument; it suggests that the drugs are a relatively new presence in the water. Therefore, the effects of these drugs might not have had time to arise.

The correct answer is D.

chrtpmdr · Answer

"However, the researchers argued that the drugs in the water were not a significant public health hazard.  They pointed out that the drug levels were so low that they could only be detected with the most recent technology , which suggested that the drugs may have already been present in the drinking water for decades"

How can D) be a proper strengthener here? The whole argument is build upon the fact that the levels were so low that they could only be detected with the most recent technology.

Although the second part of D) is strengthening the argument, isn't it a bit weird to build the argument around the assertion that "basically we've only found those levels because technology advanced" and then strengthen it with "anyway, they also found it with old technology ..."

Weird reasoning for me

mSKR · Answer

Hi  VeritasKarishma

If a drug found in drinking water is not a significant public health hazard, then how its presence in water can have discernible health effects? Can you please give some scenario?
It maybe like the person may feel weak or have dizziness even such symptoms may not bring any health hazard? Does it mean that it can not be dangerous but still can see some symptoms? Is it?

2. You mentioned that If we reverse the order then answer can be right as:
 
But how is it possible but the people have some unknown side effects?

Could you please help to give more clarity on A and A' option? I am not able comprehend the meaning precisely. What am I missing?

KarishmaB · Answer

Option (A) is given to confuse you. If it were the other way around, it would have helped us. By giving this option, they are hoping that you will fall in the trap.

Let's look at the other way around first.

- If a drug's presence in water has no discernible health effects, then it is not a public health hazard.

"Discernible" health effects means the effects that we can perceive. For example, if after drinking such water for a few days, a person gets an upset tummy or a scratchy throat, we can say that the drugs have a discernible ill effect and is a public hazard.
But sometimes, even if there are no discernible effects, a drug may be a health hazard. For example, many years of drinking such water may weaken one's immune response. Then one may catch infections easily and severely. But no one may actually be able to say that the drugs in water caused the weak immune response, at least for 20 years. After 20 years also, we don't know whether scientists would be able to discern the hazard of drugs.

Now look at the argument again:

... so drugs may have already been present in the drinking water for decades, even though they have never had any "discernible" health effects.
Conclusion - Drugs in the water are not a significant public health hazard.

Based on no discernible health effects, we are concluding no public health hazard.

We need to strengthen this. A strengthener could say that no "discernible" health effect means no health hazard. This is what reverse of (A) would have said. But what we are given is (A).

A. If a drug found in drinking water is not a significant public health hazard, then its presence in the water will not have any discernible health effects.

If a drug is not a health hazard, it will not have any discernible health effects. Well, that is pretty much what we expect. If it is not a hazard, it won't affect health. Option (A) doesn't help us. By health effect, they do mean ill health effect. A drug is unlikely to have any beneficial health effect except when prescribed as a medicine.

jabhatta2 · Answer

Hi  avigutman  - do you think this is a good question to learn from ? I was surprised this showed up because i thought the GMAT doesnt test conditional logic. I think option A is about conditional logic.

I have tried to make sense of it in my attempt below w.r.t option A specifically

Argument : A means B

A  = no discernible health effects. 
  B  = no public health hazard

In order to strengthen  
- Whenever A is seen, B is seen 
- No B means no A

Option A claims)   B means A

Thus, option A cannot be a strengthener because   B means A   is not in the list of strengtheners in red

Thus almost formulaically, one can get rid of A

Thoughts ?

jabhatta2 · Answer

Hi  avigutman  - while I agree A / B / C / E are not strengtheners -- i really dont see how D strengthen the   gap   between the premise and the conclusion whatso-ever

Per my understanding below image shows the premise and the conclusion for this argument

Strengtheners have to strengthen the 'gap' specifically. Answers that strengthen the premise are no good.

Option D just says

-- Neighboring town's water has a higher ratio (drugs / 1 unit of water) in its water compared to town X's water. 
-- This higher ratio did not show discernible health effects

All option D prooves is that   City X's water WILL NOT HAVE visible / discernible health effects obviously

But that just  strengthens the premise.   as we are already told City X's water has no discernible health effects

I dont think option D touches on the 'GAP' between   Premise : no discernible health effects   and the  conclusion : no significant public health hazard

avigutman · Answer

jabhatta2 Yes it's a good question. Yes A can be eliminated formulaically, or you can use logic to eliminate it (kind of like how algebra can be used to solve quant reasoning but you can also use reasoning instead).

avigutman · Answer

jabhatta2  
I'm pasting here from the original argument:
which  suggested  that the drugs  may  have already been present in the drinking water for decades
Answer choice D strengthens the word " may ". Does that help?

jabhatta2 · Answer

Thanks  avigutman  - just trying to solve option A formulaically -- here was my attempt with algebra (tried visualizing it).

Argument : All A are B

A = significant public health hazard.
B = discernable health effects

Option A : All B are A

A = significant public health hazard.
B = discernable health effects

Curious on your thoughts 
Thank you !

jabhatta2 · Answer

Sorry  avigutman  : i am not able to grasp how this strengthens the word  "may"  unfortunately.

Facts from Option D  
 -  Toxicity Ratio  (toxic material / 1 unit of water) of Neighboring town's water is MUCH higher compared to  Toxicity Ratio  of City X's water. 
- Even with this higher ratio, there are NO visible health effects seen from Neighboring town's water

Implication : City X's water  today  WILL  not   have any visible health effects.

But just because there is / will NOT be visible health effects seen from City X's water --> can one really say say the the " may " is MORE LIKELY ?

I dont believe one can claim THAT the " may " is more likely just beacuse  City X's water   today  WILL not have any visible health effects.

avigutman · Answer

jabhatta2  Yes, this is fine. Technically the argument relies on the idea that if there are no discernible health effects -> there's no significant public health hazard, but you're correct in rephrasing that as: significant public health hazard -> discernible health effects.
And, yes, answer choice A is out of scope because it offers the opposite direction.

Analogy:
Argument requires that all dogs are animals, and answer choice A states that all animals are dogs.

avigutman · Answer

jabhatta2  From the argument itself, we don't  know  that the drugs have already been present in the drinking water of city X for decades. If it's true, then one could argue that they are safe, since they have never had any discernible health effects.  But if it's not true, the whole argument collapses. 
Now, what does answer choice D say?
 The exact same drugs, in drinking water elsewhere, over a long period of time, led to no discernible health effects.
 Does this prove the argument?? No, of course not. 
There remain many gaps, for instance: 
(i) just because health effects aren't discernible does't mean they're not present.
(ii) if there are no discernible health effects, does that necessarily mean there's no significant public health hazard? I don't know.
Nevertheless, the  blue text above  does increase the likelihood that the presence of the drugs in the drinking water is fine ( even if it's not true that city X's public drinking water has already had these drugs for a while ).

Hoozan · Answer

KarishmaB   EducationAisle  please could you help me with the following thought process

The argument talks about low drug levels + the long duration of drugs present in public drinking water

(D) talks about the same drugs BUT it doesn't talk about its level and especially the duration of its presence in the water.

I mean, what if the drug was detected in the water BUT it was present only for one month? In that case, we can't say that the long duration of the same drug (as discussed in the argument) will not have any discernible health effects.

Note:- The research was conducted a decade ago but that doesn't mean that the drug was present in the water for a decade.

However, since the question is talking about "most strengthen" we can select (D) as the rest of the choices do not help in any way. While (D) to some extent does

KarishmaB · Answer

The degree of strength an option provides is irrelevant. We will not have two options both strengthening - one to a smaller degree, other to greater.

Also, we will need to understand the context of the question. What goes in the city's water supply is not something one can completely control. If something is not detectable, anyway one can do nothing about it. Also, the contents will depend on the source of the water and many other such factors. But one thing we know is that it is not very easy or feasible to change the water quality as per our wishes for a whole city.

D. Researchers using older, less sensitive technology detected the same drugs several decades ago in the public drinking water of a neighboring town but could find no discernible health effects.

This tells us that the tech used decades ago was less sensitive so it seems that the % of these drugs was much higher in those days for that town. Also, we don't know how long the drugs had been in the water supply before they were detected and whether the city was able to remove them from the water afterwards. All we know is that the drugs were detected though no health issues were discernible. 
So it does strengthen that the lower level of drugs present in this water will not have any discernible ill effects either.

All other options do not strengthen so are eliminated.

EducationAisle · Answer

D does talk about the "level" Hoozan.

D says:

older, less sensitive technology detected the same drugs several decades ago in the public drinking water of a neighboring town
 
This clearly means that the "level" of drugs detected (in the public drinking water of a neighboring town) was "higher" than what researchers in City X have recently discovered.

DmitryFarberMPrep · Answer

Will2020  
Others have covered this fairly well, so if there's something about A or B that's still bugging you, please let me know. However, here's how I'd explain those two:

First, we have to keep in mind what the conclusion of the argument is. The researchers have concluded that the drugs don't pose a significant public health hazard. Now let's look at how A and B relate to that claim:

A) "If a drug found in drinking water is not a significant public health hazard, then its presence in the water will not have any discernible health effects."
This actually  builds  on the claim that's already been made, so we can cut it immediately. In general, if a Strengthen choice starts with "If  ," it's wrong. We're trying to get to the conclusion, so we can't begin by accepting it as the basis for some other idea. If anything, we'd like to see the reverse--"If no health effects, then not a significant public health hazard." Then, as long as it turns out to be true that these drugs really have been present for years with no ill effects, then the argument starts to look good.
 Short takeaway:  Don't just look for answers that mention a premise and conclusion. We need something that leads us FROM the premise TO the conclusion. "If  , then  " is the ultimate strengthen. "If  , then . . . " is an immediate out.

B) "There is no need to remove low levels of pharmaceutical drugs from public drinking water unless they present a significant public health hazard."
This is also trying to build on the conclusion. The question at hand isn't "If these drugs aren't a hazard, what should we do?" It's "Are they a hazard?" We want something that indicates that they are. Discussing follow-up action is not our job. 
 Short takeaway:  Stick to the precise scope of the argument. Don't confuse an argument about what IS TRUE for one about what SHOULD BE DONE.

As a parallel case, imagine that the author is arguing that the defendant in a criminal trial is guilty, and we want to help support that. We would want an answer that helps point from the evidence presented to the conclusion of guilt. For instance, if the premise is "They had a strong motive," then a strengthen might be "A person who has a strong motive to commit a crime almost always does commit the crime." If the premise is "They were identified as the culprit by a witness," a strengthen might be "The witness is reliable" or "There aren't other potential suspects who look very similar to the defendant."

The equivalent of answer choice A above would be to say "If the defendant is guilty, they will have had a motive." That may be true, but it doesn't tell us whether the defendant actually  is  guilty. Taken to extremes, we could have this: "The defendant has two eyes. So the defendant is guilty." Would it really strengthen the argument to say "If the defendant is guilty, they have two eyes"?

The equivalent of B above would be to say "We shouldn't jail the defendant unless they are guilty." Surely that's good advice, but it tells us zero about whether they actually ARE guilty.

Hope this helps. Feel free to follow up if I can clarify.

Researchers in City X recently discovered low levels of several pharma

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GMAT Critical Reasoning (CR) Questions

Researchers in City X recently discovered low levels of several pharma

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