Logical ReasoningDifficulty: Easy

PT129 S3 Q24 Explanation

It is widely believed

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

TopicsSufficient Assumption

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Stimulus

It is widely believed that lancelets—small, primitive sea animals—do not have hearts. Each lancelet has a contracting vessel, but this vessel is considered an artery rather than a heart. However, this vessel is indeed a heart. After all, it strongly resembles the structure of the heart of certain other vessel closely resemble the muscular contractions of other animals' hearts.

What this question is testing

Sufficient Assumption

Your task

Find the assumption that, if added, guarantees the conclusion follows.

Common trap

Answers that only partly bridge the gap, leaving the conclusion unproven.

Winning move

Identify the new term in the conclusion and pick the choice that links it to the evidence.

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

The question
24.

The argument's conclusion follows logically if which one of the following

Answer choices

  1. Reversal2% picked this

    Only animals that have contracting vessels

    This answer reverses H → RCH the connection between muscular contractions and being a heart.

  2. Out of Scope1% picked this

    Some primitive animals other than lancelets have what is widely held to

    Primitive animals other than lancelets are out of scope for this argument since it is unknown whether there is any similarity between their hearts and the lancelet’s vessel.

  3. Correct86% picked this

    A vessel whose structure and actions closely resemble those of other animal hearts

    Why this is right

    This bridges the gap RSH + RCH → H between a vessel that resembles the structure and actions of a heart and a vessel that is a heart.

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

  4. Reversal9% picked this

    For a vessel in an animal to be properly considered a heart, that vessel must

    This answer reverses H → RCH the connection between muscular contractions and a vessel being a heart.

  5. Out of Scope1% picked this

    No animal that has a heart lacks

    The relationship between H → A having a heart and having an artery is irrelevant to the argument.

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