LSAT 116 – Section 3 – Question 13

LSAT 116 - Section 3 - Question 13

June 2004

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Question
QuickView		 Type Tags Answer
Choices		 Curve Question
Difficulty		 Psg/Game/S
Difficulty		 Explanation
PT116 S3 Q13
+LR
Resolve reconcile or explain +RRE
Causal Reasoning +CausR
A
64%
165
B
20%
160
C
12%
159
D
2%
156
E
2%
156
144
156
168
 +Harder 146.244 +SubsectionMedium

Up until about 2 billion years ago, the sun was 30 percent dimmer than it is now. If the sun were that dim now, our oceans would be completely frozen. According to fossil evidence, however, life and liquid water were both present as early as 3.8 billion years ago.

"Surprising" Phenomenon
Why was liquid water present back when the sun was so dim?

Objective
A hypothesis resolving this discrepancy must explain how Earth had liquid water 3.8 billion years ago. It must either identify a source of water other than the oceans or state a difference between Earth today and Earth 3.8 billion years ago that allowed the oceans to contain liquid water before the sun brightened.

A
Our atmosphere currently holds in significantly less heat than it did 3.8 billion years ago.
This explains the presence of liquid water 3.8 billion years ago. The atmosphere held more heat back then, so the oceans were not frozen despite the dimmer sun.
B
The liquid water present 3.8 billion years ago later froze, only to melt again about 2 billion years ago.
This does not explain how liquid water was present in the first place. The sun only brightened about 2 billion years ago, so the presence of water 3.8 billion years ago remains a mystery.
C
A significant source of heat other than the sun contributed to the melting of ice sheets approximately 2 billion years ago.
This widens the discrepancy by suggesting the oceans were frozen until about 2 billion years ago. It does not explain the presence of liquid water 3.8 billion years ago.
D
Evidence suggests that certain regions of ocean remained frozen until much more recently than 2 billion years ago.
This does not address the presence of liquid water 3.8 billion years ago. It implies that parts of Earth were colder than expected 2 billion years ago, but makes no mention of Earth 3.8 billion years ago.
E
When large portions of the globe are ice-covered, more of the sun’s heat is reflected and not absorbed by the earth than when only the poles are ice-covered.
This implies frozen oceans are likely to remain frozen and liquid oceans are likely to remain liquid, without addressing Earth 3.8 billion years ago. If the oceans were liquid back then, it remains unexplained why they were liquid.

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LSAT PrepTest 116 Explanations

Section 1 - Reading Comprehension

Section 2 - Logical Reasoning

Section 3 - Logical Reasoning

Section 4 - Reading Comprehension

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