Logical ReasoningDifficulty: Hard

PT108 S3 Q18 Explanation

Chelas and Stelma are required

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

TopicsMust be False

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Stimulus

Chelas and Stelma are required to leave their respective stations immediately to pursue any prisoner who attempts to escape from their sector. Furthermore, unless they are pursuing such a prisoner, Chelas and Stelma are forbidden to leave their stations until their replacements have arrived. On May 11 at 9 P.M., when Chelas was discovered that Chelas had violated these rules and Stelma had not.

What this question is testing

Must be False

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
18.

If the statements above are true, each of the following could be

Answer choices

  1. Compatible5% picked this

    Chelas and Stelma were at their respective stations at

    This doesn't hit any of the things we're looking for: C: pursued every escapee / never left otherwise S: failed to pursue an escapee / left for some other reason It's possible that someone tried to escape around 7pm. S pursued (following the rules). C stayed behind (breaking them). S returned with the prisoner by 8pm and thus they were both back at their stations at 9pm. C broke a rule, but S didn't.

  2. Compatible18% picked this

    Stelma left her station before 9 P.M. but Chelas

    This doesn't hit any of the things we're looking for: C: pursued every escapee / never left otherwise S: failed to pursue an escapee / left for some other reason It's possible that someone tried to escape around 7pm. S pursued (following the rules). C stayed behind (breaking them). S returned with the prisoner by 8pm and thus they were both back at their stations at 9pm. S left, but C didn't. So C broke a rule and S didn't.

  3. Compatible8% picked this

    Chelas left his station before 9 P.M. but Stelma

    This doesn't hit any of the things we're looking for: C: pursued every escapee / never left otherwise S: failed to pursue an escapee / left for some other reason It's possible that no one during this shift tried to escape. Thus neither C nor S should have left their station during this shift. If C did but S did not, then C broke a rule and S didn't.

  4. Correct65% picked this

    A prisoner attempted to escape from Chelas and Stelma's sector at 7 P.M. and neither Chelas nor Stelma left his or

    Why this is right

    According to this, both C & S broke a rule. When a prisoner tries to escape, they're supposed to pursue. They if C & S never left their station, then they would have both broken that rule. This must be false, since we were told that S didn't violate any rule.

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

  5. Compatible5% picked this

    A prisoner attempted to escape from Chelas and Stelma's sector at 7 P.M. and both Chelas and Stelma left

    This doesn't hit any of the things we're looking for: C: pursued every escapee / never left otherwise S: failed to pursue an escapee / left for some other reason It's possible that someone tried to escape around 7pm. S pursued (following the rules). C stayed behind (breaking them). S got back and stashed the prisoner back in his cell by 8pm. Then, C left his station around 8:15pm to just "take a stroll / clear his mind". C would have broken the rules, and S would have followed them.

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