LSAT 142 | Section 4 | Logical Reasoning: Q4

LR Question 4 Explanation

QUESTION TEXT: Paleontologists had long supposed that the…

QUESTION TYPE: Necessary Assumption

CONCLUSION: Diplodocus surely ate ground plants or underwater plants.

REASONING: Diplodocus could have eaten ground plants. It couldn’t have eaten tree plants by raising its neck.

ANALYSIS: This question plays the old trick of forcing your mind into a narrow frame. The author wants you to think that it’s only possible for a Diplodocus to eat high plants by raising it’s neck.

But there are other possibilities. The right answer shows that Diplodocus could have eaten high plants by standing on its hind legs.

___________

1. This strengthens the argument, but it’s not necessary. Diplodocus could have eaten on the ground even if its neck was unique.
   Negation: No modern ground feeding animal had a neck like Diplodocus.
2. This is a side issue. We only care about whether the neck went downwards while feeding. It doesn’t matter whether Diplodocus raised its head to a neutral position when it wasn’t feeding.
   Negation: Diplodocus fed on the ground, but raised its head to a neutral position when it wasn’t eating, and it could see fine.
3. This doesn’t matter. We already know that the neck structure of Diplodocus made it impossible for it to raise its head. This answer just adds a superfluous second reason that head raising wouldn’t work.
   Negation: Diplodocus could supply blood to a raised head, but it couldn’t raise its head due to neck issues.
4. CORRECT. The negation of this answer wrecks the argument. If there are other ways of eating high vegetation, then Diplodocus might not have eaten from the ground.
   Negation: Diplodocus had other ways of reaching high growing vegetation.
5. The argument is trying to prove that Diplodocus ate ground and underwater vegetation. This answer weakens the argument by reducing the possibilities for eating water vegetation.