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