Researchers in City X recently discovered low levels of several pharma

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.

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.

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).

I understand why choice D is a Strengthener. But, I am confused about A. How is choice A not a Strengthener. If it is that a drug that does not produce discernable health effects will not be a significant public health hazard. Please explain !

GMATIntensive
My kudos for SC tips below! I am going through your explanations at various CR questions from GMAT Advance. They are super helpful! Thank you so much.

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

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.

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.

Hi DmitryFarber! What is your take on this question? Why A and B are wrong? Tks!

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 [Conclusion]," 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 [premise], then [Conclusion]" is the ultimate strengthen. "If [Conclusion], 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.

That's an awesome explanation DmitryFarber! Thank you so much!

I did not like choice (D) because it talks about "neighboring town"

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.

Normally, we might eliminate an answer choices that talks about some other place. In other words,
the water in City X might be different than the water in neighboring town, so comparison of these two water seemed irrelevant to me.

Any thoughts?

You will definitely have to re-calibrate your reasoning with this sort of thing.
Given 2 data pools / settings / backgrounds of the same type—e.g., 2 cities, or 2 patients having the same surgery, or (as in this situation) 2 municipal water supplies—you should assume that analogies DO exist, and that evidence from one setting ••IS•• relevant to the other one, unless you are given specific reasons to conclude otherwise.

In this problem, you should assume that "the public drinking water of a neighboring town" ••IS•• relevant to the drinking water of City X.

In real life, I bet you're well aware of this.
Let's say you're considering whether to have a certain surgery. In that case, you'd look at medical data from OTHER patients who are demographically similar to you (age, sex, ethnicity)—right?
Hopefully it's obvious that those other patients' results ••ARE•• relevant to your situation, UNLESS there are medical differences between you and them that invalidate the analogy.

Yes?

If you tried to apply the same sort of reasoning you're proposing here, then you would actually end up concluding that ALL medical research is completely useless and irrelevant to you—unless you yourself were a subject of the research! That's absurd, of course; research on other subjects like you IS relevant by default.
For the same reason, the municipal water supplies of other cities in the same region are definitely relevant here.

Please take a look at this other official problem, which operates on the same type of principle.

Hi RonTargetTestPrep AnishPassi GMATNinja ReedArnoldMPREP - my question is on the argument itself - would you agree there are 3 different premises, all pointing to the same conclusion?

These 3 premises are independent of each other.

Thus the OA -- could be strengthening any of the 'assumptions' (aka'jumps) between either of the three premises and the conclusion

An assumption -- is visualized as an arrow in my screenshot

Personally, I'd structure this more as an "A and B therefore C" argument.


"There is a very low amount of drugs in the water, only detectable by special tools." (A)

AND/(Therefore? Kind of? Not a very strong therefore but the argument kind of implies it)

"Drugs could have been there for a long time, and we've seen no health effects" (B...Kind of a B1 + B2 combo)

THEREFORE

"Drugs don't pose a big health risk." (C)


My big questions on this one were:

"Is that small amount small enough to not matter?"

and

"If it has been there for a while with no health effects, has something changed that would now make it a health risk? (e.g. did we start putting something else in the water that would combine with these drugs to make it a health risk?"

So I think, more or less, the answer to your question here is 'yes,' you can look at the assumptions that join different premises to the same conclusion. Any one is worth questioning.

Thank you so much ReedArnoldMPREP - Do you see any 'relationship/connection/assumption' between (A) and Combo B [B1 + B2] ?

I think the passage does make an assumption that -- because [A] is allegedly true, Combo B [B1+ B2] IS PROBABLY true.

i.e - seems like (A) and combo B are connected as well

I say this because of the red circle in the screenshot