LSAT 158 – Section 3 – Question 19

LSAT 158 - Section 3 - Question 19

May 2020

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Question
QuickView		 Type Tags Answer
Choices		 Curve Question
Difficulty		 Psg/Game/S
Difficulty		 Explanation
PT158 S3 Q19
+LR
+Exp
Sufficient assumption +SA
Conditional Reasoning +CondR
Link Assumption +LinkA
A
14%
154
B
6%
152
C
9%
154
D
8%
154
E
63%
164
148
155
163
 +Harder 145.724 +SubsectionMedium

For there to be a thriving population of turtles in a pond, conditions at that pond must be beneficial to turtles. The water in Wallakim Pond, unlike that in Sosachi Pond, is acidic. Thus, there must not be a thriving population of turtles at Wallakim Pond.

Summary
The author concludes that there must not be a thriving population of turtles at Wallakim Pond. Why? Because of the following:
In order to have a thriving population of turtles in a pond, conditions in the pond must be beneficial to turtles.
The water in Wallakim Pond is acidic.

Missing Connection
We want to prove that there isn’t a thriving turtle population at Wallakim Pond. To do that, we want to prove that the pond doesn’t have what’s necessary for a thriving turtle population — we want to prove that the pond doesn’t have conditions beneficial to turtles.
Do we have enough to prove that? No...the other premise simply states that Wallakim Pond is acidic. But is an acidic pond something that does NOT benefit turtles? We don’t know. To make the argument valid then, we want to establish that an acidic pond is a condition that does NOT benefit turtles.

A
If the water in a pond is not acidic, the conditions at that pond are beneficial to turtles.
We want to establish that if the water IS acidic, the conditions are NOT beneficial to turtles. (A) is the sufficiency/necessity confused version of what want. It doesn’t establish when something is NOT beneficial to turtles.
B
The most important factor that determines whether a pond will have a thriving turtle population is the acidity of the water.
(B) doesn’t indicate whether acidity is something that tends to decrease the chances of a thriving turtle population or increase it. We don’t currently have any premises establishing that acidity in water is something that doesn’t benefit turtle populations.
C
The water conditions at Sosachi Pond are more beneficial to turtles than are the water conditions at Wallakim Pond.
(C) doesn’t establish that the conditions in Wallakim Pond are not beneficial to turtles. Although they are not as beneficial to turtles as the conditions are in Sosachi Pond, that does not establish that conditions at Wallakim are not beneficial.
D
Wallakim Pond would have a thriving population of turtles if it were not acidic.
(D) establishes that if Wallakim were NOT acidic, the turtle population there would be thriving. But we’re trying to show that because Wallakim IS acidic, the turtle population is NOT thriving. (D) is a sufficiency/necessity confused version of something that could have been correct.
E
The conditions at a pond are beneficial to turtles only if the water in the pond is not acidic.
(E) establishes that in order for conditions to be beneficial to turtles, the water in the pond cannot be acidic. Since the water at Wallakim Pond IS acidic, we can infer that the conditions are NOT beneficial to turtles. In connection with the first premise, we can conclude that the turtle population there is NOT thriving.

This is a Sufficient Assumption question.

The argument starts with a conditional: a thriving population of turtles in a pond requires beneficial conditions at the pond.

thriving → beneficial

Wallakim Pond, we’re told, has acidic water.

acidicw

We’re also told that Sosachi Pond doesn’t but the conclusion doesn’t care about Sosachi and so we shouldn’t either.

Finally, the conclusion says that the population of turtles at Wallakim Pond must not be thriving.

/thrivingw

Let’s put this all together.

thriving → beneficial

acidicw

_________________

/thrivingw

Looking at the conclusion, you can see that the argument is trying to contrapose on the conditional. It’s trying to fail the “beneficial” condition. If it’s successful in doing that, then we can conclude “/thriving.” But the problem is that the only other premise doesn’t hook up to “/beneficial.” We don’t know what “acidic” means for turtles. Is that beneficial for them or not? If we’re able to establish that “/acidic” is a necessary condition, then this argument becomes valid:

thriving → beneficial → /acidic

acidicw

_________________

/thrivingw

This is what Correct Answer Choice (E) gives us. It says that the conditions of a pond are beneficial only if the water is not acidic. That’s exactly what we’re looking for: beneficial → /acidic.

Answer Choice (A) says that if the water is not acidic, then the conditions are beneficial. /acidic → beneficial. That’s the sufficiency-necessity confused version of (E).

Answer Choice (B) says that the acidity of water is the most important factor that determines whether the population of turtles will be thriving. But that doesn’t tell us whether acid is good or bad. It just says it’s powerful. In which direction? Even if (B) said that it’s in the bad direction, it would merely strengthen the argument, which would still fall short of the SA requirement.

This is what we in effect get in Answer Choice (C). It says that the conditions at Sosachi are more beneficial than the conditions at Wallakim. We have to assume that all other conditions are held equal between Sosachi and Wallakim. On that assumption, we can infer that the difference is caused by the difference in their waters’ acidity. But even then, it just means that acidity is relatively less beneficial.

Answer Choice (D) says that Wallakim would have a thriving population if the water were not acidic. That translates to /acidic → thriving. But that doesn’t fit what we’re looking for.

That means it’s the acidity in the water that’s causing the population to not be thriving.

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LSAT PrepTest 158 Explanations

Section 1 - Reading Comprehension

Section 2 - Logical Reasoning

Section 3 - Logical Reasoning

Section 4 - Logical Reasoning

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