LSAT 102 – Section 4 – Question 15

LSAT 102 - Section 4 - Question 15

June 1998

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Target time: 2:04

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Question
QuickView		 Type Tags Answer
Choices		 Curve Question
Difficulty		 Psg/Game/S
Difficulty		 Explanation
PT102 S4 Q15
+LR
Must be false +MBF
Conditional Reasoning +CondR
Eliminating Options +ElimOpt
A
4%
160
B
8%
160
C
4%
161
D
11%
163
E
74%
167
142
154
165
 +Harder 146.127 +SubsectionMedium

J.Y.’s explanation

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The southern half of a certain region of the earth was covered entirely by water during the Cretaceous period, the last 75 million years of the Mesozoic era, the era when dinosaurs roamed the earth. Dinosaurs lived only on land. Thus, plesiosaurs—swimming reptiles that lived during the Cretaceous period exclusively—were not dinosaurs. No single species of dinosaur lived throughout the entire Mesozoic era.

Summary
Dinosaurs existed during the Mesozoic era. But no given species of dinosaur lived through the entire Mesozoic.

Dinosaurs lived only on land.

The Cretaceous period was at the end of the Mesozoic.

During the Cretaceous, the southern half of some region was covered by water.

Plesiosaurs were swimming reptiles that lived only during the Cretaceous.

Notable Valid Inferences
During the Cretaceous period, dinosaurs couldn’t have lived in the southern half of the region. (It was covered by water, and dinosaurs lived only on land.)

This is a Must Be False question, so any answer choice that contradicts this inference must be false.

A
Dinosaurs inhabited the northern half of the region throughout the entire Mesozoic era.
Could be true. We can infer that dinosaurs didn’t inhabit the southern half, but we’re told nothing about the northern half. It’s possible dinosaurs inhabited that region. And although no single species lived throughout the Mesozoic, it’s possible that dinosaurs as a whole did.
B
Plesiosaurs did not inhabit the southern half of the region during the Cretaceous period.
Could be true. We know plesiosaurs lived during the Cretaceous and were swimming reptiles, but we don’t know where they lived. Although the southern half of the region was covered by water, nothing suggests that plesiosaurs had to live there. They might have all lived elsewhere.
C
Plesiosaurs did not inhabit the southern half of the region before the Cretaceous period.
Must be true. Plesiosaurs lived only during the Cretaceous period, not before.
D
Dinosaurs did not inhabit the northern half of the region during the Cretaceous period.
Could be true. We don’t know anything about the northern half of the region, or where dinosaurs lived. It’s possible they all lived in other regions entirely.
E
Dinosaurs inhabited the southern half of the region throughout the entire Mesozoic era.
Must be false. The Mesozoic era includes the Cretaceous period, during which time the southern half of the region was covered entirely by water. Dinosaurs lived only on land. So dinosaurs could not have lived in the southern half of the region during that time.

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LSAT PrepTest 102 Explanations

Section 1 - Reading Comprehension

Section 2 - Logical Reasoning

Section 3 - Logical Reasoning

Section 4 - Logical Reasoning

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