Logical ReasoningDifficulty: Hard

PT116 S3 Q23 Explanation

Each of many different human

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

TopicsMain Conclusion

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Stimulus

Each of many different human hormones can by itself raise the concentration of glucose in the blood. The reason for this is probably a metabolic quirk of the brain. To see this, consider that although most human cells can produce energy from fats and proteins, brain cells can use only brain cells will rapidly starve, leading to unconsciousness and death.

What this question is testing

Main Conclusion

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
23.

Which one of the following most accurately expresses the main conclusion of

Answer choices

  1. Fact, not Opinion16% picked this

    Each of many different human hormones can by itself raise blood

    The easiest way to talk ourselves out of believing this is a conclusion is to recognize that it is being presented as an established scientific fact about our bodies. If we were to ask, why should we believe that "every hormone can by itself raise glucose"? the support would sound like Because ... in a lab, we tested adrenaline, and endocrine, and insulin, and estrogen, and every one of these hormones was able in an isolated setting to raise the level of glucose in blood. We don't have any support for the first sentence, because it's not a conclusion. It's just being presented as an established background fact.

  2. Correct62% picked this

    The reason that many different hormones can each independently raise blood glucose levels is probably a metabolic

    Why this is right

    This provides a great meaning match for the 2nd sentence, which was the Main Conclusion.

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

  3. Premise3% picked this

    Although most human cells can produce energy from fats and proteins, brain cells can produce

    This, again, is presented as an established science fact, not the author's opinion. No evidence is offered to help convince us that brain cells can produce energy only from glucose. And this claim is prefaced by a Support Indicator, "to see [that my CONCLUSION is true], consider [my evidence]"

  4. Intermediate Conclusion Last Claim Trap16% picked this

    If blood glucose levels fall too low, then brain cells starve, resulting in loss of

    The conclusion on Main Conclusion is usually not found in the final claim (unless it's an easy problem), so we want to be wary before picking an answer that looks like the last claim. As discussed in the evaluation, this claim is debatably even a reasoning conclusion. It sounds more like a science-y cause/effect claim. And either way, this claim is part of the Support for the 2nd sentence. The author is saying, "Because brains only metabolize glucose and would die without it, that's probably why every hormone has the power to raise glucose levels".

  5. Never Said3% picked this

    The reason brain cells starve if deprived of glucose is that they can produce energy

    This is an implicit Inference we can derive from reading the last two sentences, whereas on Main Conclusion we want an answer to regurgitate the explicitly drawn conclusion. Also, these last two sentences are there as support to help us "see" the truth of the 2nd sentence, which is the author's opinionated conclusion.

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