Logical ReasoningDifficulty: Hard

PT159 S3 Q19 ExplanationWhen plants are growing quickly, they take more carbon dioxide

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

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Stimulus

When plants are growing quickly, they take more carbon dioxide out of the atmosphere than they release into it. But when they are growing very slowly, the reverse is true. Any substantial increase in the amount of carbon dioxide released into the atmosphere causes temperatures to increase in the tropics, where the in the tropics, the more slowly, on average, the plants there grow.

What this question is testing

Most Supported

Your task

Break the argument into its conclusion and evidence, then do exactly what the question stem asks with that structure.

Common trap

Answers that sound relevant to the topic but don't connect to the argument's actual reasoning.

Winning move

Predict what a right answer must do, then test each choice against the conclusion-evidence gap.

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

The question
19.

Which one of the following is most strongly supported by the

Answer choices, explained

  1. Too Strong: inevitably2% picked this

    The amount of carbon dioxide released into the atmosphere will inevitably increase at a gradually

    "Inevitably" is a red flag in Most Supported questions, especially those that are not testing Conditional Logic. We also don't have any information about anything "gradually accelerating."

  2. Unsupported Causal Relationship25% picked this

    If the amount of carbon dioxide released into the atmosphere increases substantially, the bulk of Earth's plants will release more carbon dioxide into the

    A substantial increase in CO2 emissions will increase the temperature in the tropics, and that is where the bulk of Earth's plant's live, so the first half of this answer sounds like it could be correct. However, in order to say that those plants will release more CO2 than they take out, we'd need to know that they are growing very slowly. And while a substantial increase in CO2 will cause higher tropic temperatures which will in turn slow the growth of plants there on average, we can't say that it will slow them to the point where they are growing very slowly. Thus, this answer is tempting, but incorrect.

  3. Correct51% picked this

    Plants in the tropics will grow more slowly, on average, if they release enough carbon dioxide to increase substantially the total amount of

    Why this is right

    This reflects a link in our Causal Chain: Lots more CO2 > Increase Tropic Temps > Slower Ave. Growth of Tropics Plants

    Skill tested: Most Supported · how this choice captures the argument's function is the move to repeat next time.

  4. Reversal: last claim12% picked this

    If the plants in the tropics begin to grow more slowly, on average, the temperatures in the tropics will

    This answer is just a reversal of the last claim in the stimulus.

  5. Reversal: second-to-last claim11% picked this

    Any increase in temperatures in the tropics will be associated with a substantial increase in the amount of carbon

    This answer is just a reversal of the second-to-last claim in the stimulus.

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