LSAT 120 – Section 1 – Question 18

LSAT 120 - Section 1 - Question 18

October 2005

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Question
QuickView		 Type Tags Answer
Choices		 Curve Question
Difficulty		 Psg/Game/S
Difficulty		 Explanation
PT120 S1 Q18
+LR
Must be true +MBT
Conditional Reasoning +CondR
Math +Math
A
2%
155
B
14%
158
C
7%
158
D
74%
165
E
3%
155
143
153
162
 +Harder 145.819 +SubsectionMedium

In the troposphere, the lowest level of the earth’s atmosphere, the temperature decreases as one progresses straight upward. At the top, the air temperature ranges from –50 degrees Celsius over the poles to –85 degrees Celsius over the equator. At that point the stratosphere begins, and the temperature stops decreasing and instead increases as one progresses straight upward through the stratosphere. The stratosphere is warmed by ozone. When an ozone particle absorbs a dose of ultraviolet sunlight, heat is generated.

Summary
The stimulus discusses two layers of the atmosphere: the troposphere (the lowest level) and the stratosphere (the layer above the troposphere).
In the troposphere, it gets colder as you go straight up.
At the top of the troposphere, the temperature ranges from -50 degrees Celsius (over the poles) to -85 degrees Celsius (over the equator).
Once the stratosphere begins, temperature beings to increase as you go straight up.
In the stratosphere, heat is generated when an ozone particle absorbs ultraviolet sunlight.

Notable Valid Inferences
Any point in the troposphere is colder than any other point in the troposphere directly below it.
Any point in the stratosphere is warmer than any other point in the stratosphere directly below it.
A point in the stratosphere is equal temperature or warmer than the highest point in the troposphere directly below it.

A
The troposphere over the poles is thicker than the troposphere over the equator.
This could be false. We don’t know anything about the thickness of any layers of the atmosphere.
B
It is warmer at the top of the stratosphere over the poles than it is at the top of the stratosphere over the equator.
This could be false. We don’t know anything about the rate of temperature increase in the stratosphere; it could be the case that the temperature over the equator increases more quickly than the temperature above the poles.
C
The temperature in the middle part of the stratosphere over the North Pole is at least as great as the temperature in the middle part of the stratosphere over the equator.
This could be false. We only know the temperature at the point where the troposphere ends and the stratosphere begins; we don’t have enough information to compare points in the middle of the stratosphere.
D
The temperature at any point at the top of the stratosphere is at least as great as the temperature at the top of the troposphere directly beneath that point.
This must be true. We know that, in the stratosphere, the temperature increases as you go straight up. Because of this, we can infer that any point in the stratosphere is at least as high as the point below it, going all the way down to the highest point of the troposphere.
E
Depletion of the earth’s ozone layer would increase the air temperature in the stratosphere and decrease the air temperature in the troposphere.
This could be false. All we know about ozone is that it plays a role in warming the stratosphere; we have no reason to believe that removing something that generates warmth would cause the stratosphere to become warmer.

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LSAT PrepTest 120 Explanations

Section 1 - Logical Reasoning

Section 2 - Reading Comprehension

Section 3 - Logical Reasoning

Section 4 - Logical Reasoning

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