LSAT 143 – Section 3 – Question 25

LSAT 143 - Section 3 - Question 25

June 2015

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Question
QuickView		 Type Tags Answer
Choices		 Curve Question
Difficulty		 Psg/Game/S
Difficulty		 Explanation
PT143 S3 Q25
+LR
Necessary assumption +NA
Causal Reasoning +CausR
Quantifier +Quant
A
58%
167
B
7%
159
C
27%
161
D
4%
158
E
4%
158
154
162
170
 +Hardest 147.721 +SubsectionMedium

The populations of certain species of amphibians have declined dramatically in recent years, an effect many scientists attribute to industrial pollution. However, most amphibian species’ populations vary greatly from year to year because of natural variations in the weather. It is therefore impossible to be sure that the recent decline in those amphibian populations is due to industrial pollution.

Summary
The author concludes that we can’t be sure the recent decline in certain amphibian populations is due to industrial pollution.
Why?
Because most amphibian species populations vary greatly from year to year due to natural weather variations.

Notable Assumptions
The author assumes that the decline in certain amphibian populations is within the range that could be explained by natural weather variations.
The author also assumes that the certain amphibian populations we’re talking about are among the “most” species whose populations are known to vary greatly due to weather variation.

A
The amphibian species whose population declines have been attributed by many scientists to industrial pollution are not known to be among those species whose populations do not vary greatly as a result of natural variations in the weather.
Necessary, because if this were not true — if the amphibian species we’re talking about ARE known to be among the species whose populations don’t vary due to weather — then the author’s premise does not support the conclusion. If (A) were negated, natural weather variations wouldn’t be relevant to the amphibian species’ decline anymore.
B
The variations in amphibian species’ populations that result from natural variations in the weather are not always as large as the amphibian population declines that scientists have attributed to industrial pollution.
Not necessary, because the negation of (B) helps the author’s argument. If the variations in populations that result from weather variation ARE always as large as the population declines that others attribute to pollution, then that’s even more reason to think natural weather variations could be the explanation for the population decline.
C
Either industrial pollution or natural variations in the weather, but not both, caused the amphibian population declines that scientists have attributed to industrial pollution.
Not necessary, because the author never actually takes a position on what caused or didn’t cause the decline in the population. The author’s just saying that we can’t be sure it’s industrial pollution. But it might be industrial pollution, weather, or something else entirely that is the true cause.
D
If industrial pollution were reduced, the decline in certain amphibian populations would be reversed, and if industrial pollution increases, the decline in certain amphibian populations will be exacerbated.
Not necessary, because the author’s not committed to industrial pollution as the cause of the species’ population decline. The author doesn’t have to think industrial pollution has anything to do with the decline.
E
If industrial pollution is severe, it can create more variations in the weather than would occur naturally.
Not necessary, because the author never suggests any causal connection between pollution and weather variation.

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LSAT PrepTest 143 Explanations

Section 1 - Logical Reasoning

Section 2 - Reading Comprehension

Section 3 - Logical Reasoning

Section 4 - Logical Reasoning

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