Mud from a lake on an uninhabited wooded island in northern Lake Super

Question

Mud from a lake on an uninhabited wooded island in northern Lake Superior contains toxic chemicals, including toxaphene, a banned pesticide for cotton that previously was manufactured and used, not in nearby regions of Canada or the northern United States, but in the southern United States. No dumping has occurred on the island. The island lake is sufficiently elevated that water from Lake Superior does not reach it.

The statements above, if true, most strongly support which of the following hypotheses?

(A) The waters of the island lake are more severely polluted than those of Lake Superior.
(B) The toxaphene was carried to the island in the atmosphere by winds.
(C) Banning chemicals such as toxaphene does not aid the natural environment.
(D) Toxaphene has adverse effects on human beings but not on other organisms.
(E) Concentrations of toxaphene in the soil of cotton-growing regions are not sufficient to be measurable.

generis · Accepted Answer

So we have a "strengthen" question. Assume the prompt's statements are true. The statements strengthen which 
hypothesis the most?

Evidence/Premises in the prompt:  
 
• a toxin exists in a small lake on an island located in Lake Superior, which is in the northern part of the U.S. and in Canada

• the toxin was not manufactured or used in the northern U.S., Canada, or nearby regions

• the toxin WAS manufactured and used in the southern U.S. as a pesticide for cotton plants

• Water from Lake Superior cannot reach water in the little lake (and vice versa) because the 
island rises too high above the surface of Lake Superior

• The island is 
-- uninhabited (no one lives there)
-- not a dumping ground (no waste dumping has occurred on the island)
-- thickly wooded (covered with trees)

Inferences to be drawn from the prompt's statements

1) Inference: The toxins in the lake did not come from its surroundings. The toxin was not 
made or used anywhere near the lake.

2) Inference: human beings did not put the toxin into the island's lake
No one lives on the island.
The island has not been a dumping ground for waste.
The toxin is now banned.

3) Inference: The toxin did not get into the little lake from Lake Superior
Water in Lake Superior cannot reach water in the little lake and vice versa

The toxin might be in Lake Superior. We do not know.
It does not matter. We know that Lake Superior is not the mechanism
by which the toxin got into the little island lake.

4) Inference that is also the LOGICAL ISSUE or GAP: the  toxin should not be in that island lake , 
but it is, and  it got there by some mechanism .

HOW  DID THE TOXIN GET IN THE LITTLE LAKE'S WATER?

See whether you can form a hypothesis.   
How would a toxin get from the southern U.S. to this northern island's waters?
  After an aspirant is fairly familiar with CR questions, forming hypotheses or tentative answers in CR is the single best way I know to get better at CR.  * 
(Most of the time, do  not  form hypotheses in paradox or disparity questions. Usually too many possibilities exist, and using the answer choices is much more efficient.)

The prompt's sentences eliminate a lot of possible mechanisms.

There is one medium-sized hint (#1) and one tiny hint (#2):
1) the toxin was used as a pesticide for cotton plants in the south, and
2)  trees  grow on the island. (It is "wooded.")

Skim the answers. 
  Only one hypothesis directly, sensibly, and logically addresses
HOW the toxin    got from the southern U.S. to a lake in the north

Simultaneously, only one answer's hypothesis is most strongly supported by the prompt's statements

(A) The waters of the island lake are more severely polluted than those of Lake Superior.
  INCORRECT - too narrowly focused, does not address the main issue in
the prompt, is not supported logically by the prompt's statements

First, the hypothesis is too narrowly focused on levels of toxins in the lakes.

Second, this hypothesis is without support from the prompt (see analysis below)

Third, this hypothesis offers no theory that might explain how the toxin got into the island lake.

HOWEVER . . . This hypothesis might be a tempting answer.

Temptation: We  can  infer something from the fact that the water in
Lake Superior does not reach the water in the little lake.

But the inference this hypothesis requires is the wrong one, and is supported by zero evidence.

What is this   unsupported inference/conclusion?

Lake A is polluted and isolated from Lake B. Lake A cannot dump its toxin into Lake B. 
Faulty reasoning:  THEREFORE  there is less pollution in Lake B than in Lake A.
Stated differently, there is more pollution in the little lake than in Lake Superior.

100% wrong. The pollution in Lake A and levels of more or less pollution in Lake B have no logical connection.
No evidence in the prompt supports this conclusion. In fact, the prompt says NOTHING about the pollution levels of Lake B.

I will reverse this hypothesis. My hypothesis is just as valid as Option A.
  Pretend Option A:  
 The waters of Lake Superior are more severely polluted than the waters of the island lake.

Is it possible that Lake Superior is  more  polluted than the little lake? Yes, it is possible. Why?
We do not know anything about pollution levels in Lake Superior. At all. Lake Superior could
be less polluted than the island lake. It could be more polluted.

The ability to make an equal case for two contradictory statements based on the same evidence
-- the prompt's statements -- is never a good sign.

From the prompt's statements, we cannot infer anything about
-- whether the water in Lake Superior is polluted with this toxin
-- whether the water in Lake Superior is MORE or LESS polluted with this toxin
-- whether the water in Lake Superior is polluted at all

We can make only one inference  from the statement 
that the water in Lake Superior cannot reach the water in the little lake.

Here is the one inference: the water in Lake Superior 
was not the mechanism that delivered the toxin to the little lake.  The end.

In addition to being narrowly focused, logically incoherent, and
conclusive of nothing in the prompt, does this option hypothesize 
about how the toxin got in the little lake? No.

This hypothesis is not supported by the statements, let alone strongly supported.
ELIMINATE

(B) The toxaphene was carried to the island in the atmosphere by winds.

On the money.   This option gives the answer to, "How did the toxin get from the southern
U.S. to an island in the northern U.S.?"

This hypothesis offers a theory about the toxin's delivery mechanism from
the southern U.S. to the little northern lake.

By what mechanism did the toxin get into the little lake? ATMOSPHERIC WINDS.

Between prompt and hypothesis a clear logical link exists.

We can tease it out a bit. The prompt's statements lay out a fact pattern

Problem X exists in Place Q.

A, B, C, and D did not cause problem X.

However, some Xs were made and used in Place P at one time.

Implication: The Xs traveled from Place P to Place Q.
The question: HOW?

This hypothesis both follows from the implication of the prompt's statements
and answers the logical question.

Toxins in a small lake in the northern U.S. should not be there.

Other delivery mechanisms have been eliminated by statements in the prompt.

The mechanism by which the toxin was delivered into the little lake was not regional dispersion; 
not Lake Superior; not human beings; and not dumping of waste.

The toxin was made and used in the southern U.S. as a pesticide on cotton plants. 
Cotton plants grow outdoors.

Hypothesis? The toxin was carried from plants in the southern U.S. to the island 
in the north by atmospheric winds. (Trees grow on that island. Vegetation "catches" particles in the wind.)

THAT hypotheses is strongly supported by every statement in the prompt.
  CORRECT

(C) Banning chemicals such as toxaphene does not aid the natural environment.
  INCORRECT. Too general, does not address the prompt's main point

This hypothesis is too general. The prompt's statements say nothing directly about 
general bans on chemicals and those bans' effect on the natural environment.

This hypothesis does not respond to the logical problem presented by the
prompt's statements.

Does a ban's inefficacy explain how the toxin got in the northern lake? No. 
The toxin was not used in the north. 
Whether bans on chemicals help the environment is pretty hard to assess in a region where the chemicals were not used.

In one indirect sense, the general idea of the prompt supports this hypothesis.
Despite a ban on this chemical, the chemical got into water far from the region where the chemical was used.

Can we conclude generally that bans do not help the environment?
No. We have no evidence from the prompt about what happened in the southern U.S., for example.

Can we conclude specifically that this ban on this chemical did not help this environment?
Yes, in a limited way we can conclude that the ban on this chemical did not help this environment --
at least not completely.

We cannot go further than a limited "maybe," however.
The prompt says nothing about other bans on other chemicals.
It says nothing about whether the toxin levels would be worse without the ban.
It says nothing about whether the toxin levels would be better without the ban. (Unlikely.)

Most of all, we cannot generalize about all bans' effects on the environment from one case.

The prompt does not support this hypothesis. If the ban failed to help the environment,
we still have no idea how the toxin got into a region where the toxin was not used.
If the ban did help the environment, we still have no idea how the toxin got into a region where
the toxin was not used.

This hypothesis is disconnected from the prompt's statements, and it overgeneralizes.
ELIMINATE

(D) Toxaphene has adverse effects on human beings but not on other organisms.
  INCORRECT off topic/out of scope, not relevant, too specific, does not address main point   
WTH?   This one is a gift from GMAC.   Take it and   toss it.

The prompt's statements contain  no  mention of adverse effects, human beings, or other organisms.

Does this option help explain how the toxin got into the little island's lake water (such that it might 
be a supported hypothesis)? Nope.
ELIMINATE

(E) Concentrations of toxaphene in the soil of cotton-growing regions are not sufficient of be measurable.
  INCORRECT. Irrelevant, not responsive to the prompt's main point   
Another throwaway gift.

Nothing in the prompt's statements suggests that: 
1) the inability to measure of toxin levels in one region causes the presence of toxins in another region; or
2) whether toxins can be measured is an issue at all.

If anything, the prompt's statements dispense with the issue.
One statement says that a small lake contains toxaphene. 
The author either measured toxin levels or learned about them.
In both cases, she believed the measurement. Quantifiability of toxin levels in soil is a non-issue.
 
Finally, check again: does this hypothesis help to explain the missing logical link
in the prompt's statements?

If the toxin were not measurable in soils in the southern U.S. . . .
would that deficiency explain the presence of the toxin in the lake? Nope.

This hypothesis is not supported by statements in the prompt. 
ELIMINATE

ANSWER B

Hope this helps.

*I took the LSAT (and graduated from an elite law school). Of the 100 questions on the LSAT, HALF are logical reasoning ("LR"). I agree with an expert who described LR as "CR on steroids." I deeply recommend practice in order to get better at anticipating answers. The people who write these tests are trying to knock you off your game, including the anticipation game, at which you are skilled. Don't give them the pleasure.

sssanskaar · Answer

Hi experts, I don't think this is a strengthen question. There is no conclusion in the argument. Rather, this is an inference question as we have to find out the best conclusion.

Given that, I don't understand how option B can be the answer. Nowhere in the argument, it is mentioned that there are winds flowing. Had this question asked for a strengthener, this option would have been a great choice. But since we have to see from the point of inference, we can't verify if the toxins were transmitted via winds. A better choice would have been - 
"Toxins must have been transferred to the lake in the islands  by some other means. "

Out of all the options, I think option A suits the best of the inference category because 
 Mud from a lake on an uninhabited wooded island in northern Lake Superior contains toxic chemicals

and

The island lake is sufficiently elevated that water from Lake Superior does not reach it.

experts, please confirm.  egmat   GMATNinja   sayantanc2k

akifbaykal · Answer

Actually I used the choice elemination ways.
So I eleminated A,C,D and E due to being out of scope.
So I believe that answer is B

BrentGMATPrepNow · Answer

PREMISE: Island lake contains toxic chemicals 
PREMISE: The chemicals were not dumped in the lake, and water from Lake Superior cannot reach the lake

We want to find the most reasonable conclusion that follows from this information

(A) The waters of the island lake are more severely polluted than those of Lake Superior. 
The passage does not contain any information regarding the pollution levels of Lake Superior. 
Eliminate A

(B) The toxaphene was carried to the island in the atmosphere by winds.
The passage tells us that there is toxaphene in the lake, and it also tells us that the chemical could not have reached the lake via two methods. So  the chemical must be reaching the island lake in some other way . This answer choice suggests one of those possible ways. Although it's only one possible way for the chemical to reach the lake, we cannot dismiss it. So we will leave answer choice B for now

(C) Banning chemicals such as toxaphene does not aid the natural environment. 
There is nothing in the passage that would suggest that this is true. If anything, it seems that banning toxaphene WOULD help the environment. 
Eliminate C

(D) Toxaphene has adverse effects on human beings but not on other organisms.
There is nothing in the passage that supports this claim. 
Eliminate D

(E) Concentrations of toxaphene in the soil of cotton-growing regions are not sufficient of be measurable 
There is nothing in the passage that supports this claim. 
Eliminate E

By the process of elimination we are left with only one answer choice.

Answer: B

Cheers, 
Brent

GMATNinja · Answer

As you stated, we’re looking for an answer choice that is supported by the statements in the passage. With that in mind, let’s take a look at (A):

The passage indicates that the island lake contains toxic chemicals, including toxaphene, but we have no reason to believe that Lake Superior does not contain toxic chemicals as well. Sure, the water from Lake Superior does not reach the island lake because the island lake is elevated, but this does not mean that water (and, consequently, toxic chemicals) cannot flow down from the island lake into Lake Superior. Additionally, the toxic chemicals could reach Lake Superior another way.

Moreover, (A) states that the island lake is more  polluted  than Lake Superior. That’s different than stating that it has more  toxic chemicals , or even toxaphene, than Lake Superior. It’s possible, and perhaps even likely due to its close proximity to civilization, that Lake Superior contains additional pollutants, apart from those found in the island lake. This means that Lake Superior could reasonably be as polluted as or more polluted than the island lake, and we can eliminate (A).

And here’s (B):

The passage stated that mud from an island in the region of the northern US and Canada contains toxaphene, a chemical used in the southern US. This introduces the question of how the chemical got from the southern US to an island lake in the much further north. The remainder of the passage eliminates the possibility that the chemical was dumped on the island, and it eliminates the possibility that the chemical seeped into the island lake by way of the water in Lake Superior surrounding it (due to the island lake’s elevation).

All this serves to support the idea that there must be an alternative explanation as to how the toxaphene traveled from the southern US to the island lake. (B) presents a possible explanation: winds carried the toxaphene to the island. Although we can’t be certain that this hypothesis is true, it is strongly supported by the passage that eliminates the possibility of alternative explanations. For that reason, (B) is correct.

I hope that helps!

shanks2020 · Answer

Hi  GMATNinja   AndrewN

As you mentioned, the correct answer is "One of the possibilities". So do you think this question is an exception, bcoz in inference type questions, we generally expect a "Must be true" answer". But here the inference is "Can be true". There could be other ways to reach the lake, just that we don't know all. Had this option been like "alternative way apart from water or dumping" then it would have been a must be true condition.

AndrewN · Answer

I see the task a little differently,  shanks2020 . Take a look at the  exact  phrasing of the question again (my  emphasis ):

Most strongly support  is not synonymous with  must be true . As a related aside, I remember when I visited Hawai'i, a tour guide informing the group of the three W's whereby flora and fauna could be introduced to the island: wind, wings, and water. Could it be the case here that some flying organism, perhaps large flocks of migratory waterfowl, introduced toxins into northern Lake Superior? Sure. But I do not see an answer choice that even closely resembles such a hypothesis. Although I am not overly fond of the definitive language in   was  carried  in (B), a hypothesis can be put forth in such a manner. Finally, and perhaps most importantly, I could not get behind any other answer as more reasonable than (B), which is why I ended up choosing it.

I hope that helps. Thank you for thinking to ask me.

- Andrew

Vatsal7794 · Answer

generis  Thanks for the awesome explanation.

Kratosgmat · Answer

For B there was no dumping on the island then, how did the toxins reach there? they were probably carried by the winds.
For A even though the question says its a hypothesis we cant arrive at the conclusion that waters of island are more severely polluted than those of Lake superior (we dont have any info about lake superior to arrive at this conclusion/ hypothesis)

Joe258 · Answer

Must have been the wind! - B

The passage states: a toxic substance is presence in an uninhabited island, high elevation - cannot be from Lake Superior, and it's usage is likely not from that Northern region, and no dumping - no human intervention. All of this point to some possible causes of the presence of that substance, and wind is one of them. 
A - We don't even know whether that substance is a pollutant or not, and plus, it's in the mud.
C - Again, we don't know if the substance is a pollutant to the region or not. How is banning it to aid the nature is supported?
D - Nowhere in the passage discusses the effects of this substance on human. At the very least, it should subtly help human in eliminating pests. But that's too far.
E - Whether the substance is measurable or not in cotton-growing soils is not the point the passage supports.

sriramsundaram91 · Answer

If you have not noted that Lake superior is between the north of the united states + canada and the south of the united states, you won't be able to reach the conclusion that the only way for the toxin to reach is via winds.
Because cotton + pesticide was used in the south, so how did it reach the north? there is water body between, so winds.

Mud from a lake on an uninhabited wooded island in northern Lake Super

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Mud from a lake on an uninhabited wooded island in northern Lake Super

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