Logical ReasoningDifficulty: Easy

PT136 S2 Q5 Explanation

Bacteria that benefit human beings

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

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Stimulus

Bacteria that benefit human beings when they are present in the body are called commensals. The bacterium Helicobacter pylori plays a primary role in the development of stomach ulcers. But since stomach ulcers occur in less than 10 percent of those harboring H. pylori, and since it allegedly strengthens immune response, many cause tuberculosis—get sick from it, yet no one would call M. tuberculosis a commensal.

What this question is testing

Weaken

Your task

Find the choice that makes the argument's conclusion less likely to be true.

Common trap

Answers that look negative but attack a claim the argument never relied on.

Winning move

Find the assumption the argument depends on, then pick the choice that undermines it.

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

The question
5.

Which one of the following, if true, most seriously undermines the

Answer choices

  1. Strengthen2% picked this

    Stomach ulcers caused by H. pylori and tuberculosis can both be effectively

    This supports the comparison between M. tuberculosis and H. pylori.

  2. Too Weak2% picked this

    Cases of tuberculosis usually last longer than ulcers caused by

    While this provides a difference between H. pylori and M. tuberculosis, it does not do so on the key point of providing a benefit.

  3. Correct87% picked this

    People who harbor M. tuberculosis derive no benefit from

    Why this is right

    This weakens the comparison by distinguishing M. tuberculosis from H. pylori in that M. tuberculosis would not benefit people, while H. pylori is known to strengthen the immune system.

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

  4. Too Weak4% picked this

    There are more people who harbor M. tuberculosis than people who

    While this provides a difference between H. pylori and M. tuberculosis, it does not do so on the key point of providing a benefit.

  5. Too Weak5% picked this

    There are more people who harbor H. pylori than people who

    While this provides a difference between H. pylori and M. tuberculosis, it does not do so on the key point of providing a benefit.

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