LSAT 69, Logical Reasoning I, Q10

LSAT 69 Explanations

LR Question 10 Explanation

QUESTION TYPE: Most Strongly Supported

FACTS: Nahcolite formed in salty lates during the Eocene. Labs tests show that nahcolite can only form in salt water where there is 1,125 PPM CO2.

ANALYSIS: Since lab results show that nahcolite formed in salt water during the Eocene, it’s probable that there was 1,125 PPM CO2 during the Eocene.

This is a ‘most strongly supported’ and not a ‘must be true’ because it’s possible the lab results are wrong.


  1. We have no reason to think that CO2 was lower for most of the 50 million years since the Eocene.
  2. We have no reason to believe CO2 levels changed during the Eocene.
  3. We have no information about lakes in general. We just know that some salty lakes had nahcolite.
  4. CORRECT. This is probably true, because nahcolite needs 1,125 PPM to form in salty lakes.
  5. We don’t know much about nahcolite. Maybe it forms easily in non-salty lakes, no matter what CO2 levels are. We have no reason to believe Nahcolite only formed in the Eocene.

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