LSAT 102 | Section 3 | Logical Reasoning: Q4

LR Question 4 Explanation

QUESTION TEXT: Scientists analyzing air bubbles that had been trapped…

QUESTION TYPE: Weaken

CONCLUSION: Ferrous material caused an increase in the population of antarctic algae.

REASONING: During the last ice age, there was a lot of ferrous material, but not much carbon dioxide. Algae absorb carbon dioxide.

ANALYSIS: The scientist speculated that ferrous material led to more algae.

But answer choice D shows no evidence that the number of diatoms (shells left by algae) increased.

___________

1. So? This is just a fact about diatoms. This doesn’t change whether diatoms can suck carbon dioxide from the atmosphere.
2. This supports the argument. It helps establish that ferrous material really could cause algal growth.
3. Of course…dust has lots of things in it. As long as dust does have ferrous material, the argument can work.
4. CORRECT. This evidence directly contradicts the hypothesis. If there were more algae, we would expect to see diatoms.
5. This supports the argument. The argument claimed that ferrous material helped algae grow.

Recap: The question begins with “Scientists analyzing air bubbles that had been trapped”. It is a Weaken question. Learn more about LSAT Weaken questions in our guide to LSAT Logical Reasoning question types.