Logical ReasoningDifficulty: Medium

PT16 S3 Q12 Explanation

The retina scanner, a machine

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

TopicsNecessary Assumption

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Stimulus

The retina scanner, a machine that scans the web of tiny blood vessels in the retina, stores information about the pattern formed by the blood vessels. This information allows it to recognize any pattern it has previously scanned. No two eyes have identical patterns of blood vessels in the retina. A retina whether it has ever scanned a retina of that person before.

What this question is testing

Necessary Assumption

Your task

Find the assumption the argument requires in order for its conclusion to hold.

Common trap

Answers that would help the argument but aren't strictly required (sufficient, not necessary).

Winning move

Negate each choice — the right one breaks the argument when negated.

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

The question
12.

The reasoning in the argument depends upon

Answer choices

  1. Correct80% picked this

    diseases of the human eye do not alter the pattern of blood vessels in the retina in ways that would make the

    Why this is right

    Answer A is correct.

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

  2. Trap12% picked this

    no person has a different pattern of blood vessels in the retina of the left eye than in the

  3. Trap3% picked this

    there are enough retina scanners to store information about every

  4. Trap2% picked this

    the number of blood vessels in the human retina is invariant, although the patterns they form differ

  5. Trap2% picked this

    there is no person whose retinas have been scanned by two or more

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