This boulder is volcanic

A free, expert breakdown of this official LSAT Logical Reasoning question.

TopicsWeaken

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Stimulus

This boulder is volcanic in origin and yet the rest of the rock in this area is sedimentary. Since this area was covered by southward-moving glaciers during the last ice age, this boulder was from its geological birthplace, by a glacier.

What this question is testing

Weaken

Your task

Find the choice that makes the argument's conclusion less likely to be true.

Common trap

Answers that look negative but attack a claim the argument never relied on.

Winning move

Find the assumption the argument depends on, then pick the choice that undermines it.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question

Which one of the following, if true, most seriously undermines the conclusion drawn in

Answer choices

Out of Scope16% picked this
Most boulders that have been moved by glaciers have not been moved more
Other boulders are not relevant to the argument.
16%
Irrelevant Relationship8% picked this
The closest geological source of volcanic rock is 50 miles south
The boulder need not have traveled here from the nearest geological source.
8%
Irrelevant Relationship6% picked this
The closest geological source of volcanic rock is 50 miles north
The boulder need not have traveled here from the nearest geological source.
6%
Correct66% picked this
There are no geological sources of volcanic rock north of
Why this is right
This weakens the argument by attacking the argument’s assumption.
Skill tested: Weaken · how this choice captures the argument's function is the move to repeat next time.
66%
Out of Scope3% picked this
No other boulders of volcanic origin exist within 50 miles of
Other boulders are not relevant to the argument.
3%

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