Logical ReasoningDifficulty: Easy

PT113 S3 Q2 Explanation

For the last three years, entomologists

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

TopicsNecessary Assumption

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Stimulus

For the last three years, entomologists have been searching for a parasite to help control a whitefly that has recently become a serious crop pest. Believing this new pest to be a variety of sweet-potato whitefly, the entomologists confined their search to parasites of the sweet-potato whitefly. Genetic research now shows the the search for a parasite has so far been wasted effort.

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
2.

Which one of the following is an assumption on which the

Answer choices

  1. Trap1% picked this

    All varieties of the sweet-potato whitefly are serious

  2. Trap1% picked this

    If a crop pest has a parasite, that parasite can always be used to

  3. Trap2% picked this

    The chances of successfully identifying a useful parasite of the new pest have increased since the proper

  4. Correct90% picked this

    No parasite of the sweet-potato whitefly is also a parasite of

    Why this is right

    Answer D is correct.

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

  5. Trap5% picked this

    In the last three years, the entomologists found no parasites of

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