LSAT 106 – Section 1 – Question 14

LSAT 106 - Section 1 - Question 14

June 1999

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Question
QuickView		 Type Tags Answer
Choices		 Curve Question
Difficulty		 Psg/Game/S
Difficulty		 Explanation
PT106 S1 Q14
+LR
Must be true +MBT
Conditional Reasoning +CondR
A
2%
156
B
91%
168
C
3%
157
D
4%
160
E
0%
141
148
155
 +Medium 152.148 +SubsectionHarder

The axis of Earth’s daily rotation is tilted with respect to the plane of its orbit at an angle of roughly 23 degrees. That angle can be kept fairly stable only by the gravitational influence of Earth’s large, nearby Moon. Without such a stable and moderate axis tilt, a planet’s climate is too extreme and unstable to support life. Mars, for example, has only very small moons, tilts at wildly fluctuating angles, and cannot support life.

Summary
The Earth’s large moon is necessary to keep the Earth’s axis tilt angle stable. This stability is necessary for the Earth to support life. Mars lacks a large moon and does not have a stable axis tilt angle. Mars cannot support life.
The stimulus can be diagrammed as follows:

Notable Valid Inferences
Without the Earth’s moon, the Earth would not be able to support life. Mars lacks a necessary condition for life—a stable axis tilt angle. This ensures Mars cannot support life.

A
If Mars had a sufficiently large nearby moon, Mars would be able to support life.
This could be false. A large moon may stabilize Mars’s axis tilt angle, fulfilling a necessary condition for life on Mars. However, this does not mean Mars fulfills any other conditions for supporting life. A stable axis tilt angle is necessary for life—not sufficient.
B
If Earth’s Moon were to leave Earth’s orbit, Earth’s climate would be unable to support life.
This must be true. As shown below, when we take the contrapositive of the conditional claims in the stimulus, we see that the absence of the Moon would mean the Earth would be unable to support life. In other words, the Moon is necessary for Earth’s ability to support life.
C
Any planet with a stable, moderate axis tilt can support life.
This could be false. A stable axis tilt angle is a necessary condition for a planet’s ability to support life—not a sufficient one.
D
Gravitational influences other than moons have little or no effect on the magnitude of the tilt angle of either Earth’s or Mars’s axis.
This could be false. While the stimulus focuses on moons and their impact on the planets’ axis tilt angles, it does not suggest that moons are the only important factor affecting the planets’ axis tilt angles.
E
No planet that has more than one moon can support life.
This could be false. We know Mars has very small moons and cannot support life. Given the information in the stimulus, however, it could be true that a planet has multiple moons with at least one large enough to keep the planet’s axis tilt angle stable.

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LSAT PrepTest 106 Explanations

Section 1 - Logical Reasoning

Section 2 - Logical Reasoning

Section 3 - Logical Reasoning

Section 4 - Reading Comprehension

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