A favored theory to explain

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

TopicsNecessary Assumption

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Stimulus

A favored theory to explain the extinction of dinosaurs, together with many other species, has been the globally catastrophic collision of a large asteroid with the Earth. Supporting evidence is an extraterrestrial chemical element in a layer of dust found worldwide at a geological level laid down contemporaneously with the supposed event. flows that occurred within the same time period as the supposed asteroid impact and the extinctions.

What this question is testing

Necessary Assumption

Your task

Find the assumption the argument requires in order for its conclusion to hold.

Common trap

Answers that would help the argument but aren't strictly required (sufficient, not necessary).

Winning move

Negate each choice — the right one breaks the argument when negated.

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

The question

15.

The new theory assumes

Answer choices

Correct89% picked this
the massive volcanic activity was not caused by the impact of
Why this is right
Answer A is correct.
Skill tested: Necessary Assumption · how this choice captures the argument's function is the move to repeat next time.
89%
Trap3% picked this
no individual dinosaurs survived the impact of the asteroid, if
3%
Trap2% picked this
the extinctions took place over a longer time period than they would have if caused by the
2%
Trap3% picked this
other volcanic eruptions were not occurring at the same time as those in
3%
Trap3% picked this
it is not possible to determine which would have occurred first, the volcanic flows in the Deccan region or the
3%

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