PrepTest 104

[lcid:3515] Prep Test 104 LSAT — Logical Reasoning — S4 Logical reasoning

Question prompt

Unplugging a peripheral component Remaining source text redacted.
Why the credited answer is right

Credited answer: B

The notes below walk through why it fits the stem and how to eliminate the rest.

Argument or Facts

Argument

Valid or Flawed

Flawed

Question Type

Errors in Reasoning Questions

Stimulus Summary

Unplug a mouse → Programs that rely on a mouse are unusable
Fred’s computer - A program requiring a mouse is unusable
Conclusion - Fred’s mouse is unplugged

Answer Anticipation

When an Errors in Reasoning stimulus features conditional logic, there’s a good chance that the correct answer will deal with a Sufficient/Necessary flaw.
Here, the argument starts with a conditional statement - if a mouse is unplugged, then software that uses a mouse is unusable. It then attempts to apply that to a specific case - that of Fred’s computer.
On Fred’s computer, a program that requires a mouse is unusable. In other words, the necessary condition of the conditional is established. From that, it concludes that his mouse is unplugged - the sufficient condition. That’s an illegal reversal, treating a necessary condition as a sufficient one. Let’s find an answer stating that.

Answer choices

  1. A
    It contains a shift Remaining source text redacted.
    Why choice A is not credited
    There’s no shift in the use of “unusable” - there’s no indication that the initial use refers to something that’s permanent.

  2. B
    It treats an event Remaining source text redacted.
    Why choice B matches the stem
    This answer has Sufficient/Necessary language, so it’s in play, but it also has causal language, so we need to check to see if that’s backed up. Does the stimulus say that one event causes a certain result? It does - unplugging a peripheral “renders” (i.e., causes) a certain result - programs to be unusable. Does the argument treat unplugging a peripheral as necessary to making a program unusable? Yep - that’s the reversal. Looking at our summary, you can see that the argument is assuming this conditional: Program requiring a peripheral unusable → Peripheral unplugged. This answer correctly describes the illegal reversal in the stimulus, so it’s the correct answer.

  3. C
    It introduces information unrelated Remaining source text redacted.
    Why choice C is not credited
    The program on Fred’s computer being unusable is related to the conclusion about a mouse being unplugged - the conditional rule in the opening line relates them. The issue isn’t that it’s unrelated, but rather that it doesn’t guarantee the conclusion is true.

  4. D
    It attempts to support Remaining source text redacted.
    Why choice D is not credited
    The generalization that is cited is the opening conditional, but there’s no indication that it’s too broad, so we can eliminate this answer.

  5. E
    It overlooks the possibility Remaining source text redacted.
    Why choice E is not credited
    The argument is about those that do require peripherals, and a specific program that requires a mouse, so these other programs are out of scope.

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