Agriculture researcher: Because of its slow

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

TopicsNecessary Assumption

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Stimulus

Agriculture researcher: Because of its slow decomposition, paper is ineffective as a mulch to guard against soil erosion. However, a mixture of paper and manure, which decomposes faster than paper alone, is very effective. When spread over test plots, the mixture significantly decreased the amount of soil erosion. Since paper better off using this mixture than paper or manure alone.

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

The agriculture researcher's argument is flawed because it provides no

Answer choices

Not as Strong an Objection3% picked this
paper by itself does not contribute to
If paper by itself does contribute to soil erosion, does that weaken the argument? Yeah, a little bit. It would again make us wonder whether we'd be better off just using manure alone. It would strengthen the idea that paper/manure mix is better than paper alone, though, so it's weird to talk about its impact. It strengthens half the conclusion and weakens half the conclusion. The weakening effect of this negation is not as strong as that of the correct answer.
3%
Contradicted: Did Not Provide Evidence4% picked this
mulch containing paper and manure works better than mulch containing
We explicitly got evidence that mulch with only paper is ineffective, whereas mulch containing paper and manure is very effective.
4%
Correct83% picked this
mulch containing paper and manure works better than mulch containing
Why this is right
This was the missing comparison we spotted. If we negated this answer, it would say "mulch with a mix of paper/manure does not work better than mulch with manure alone", which would weaken so much it would essentially contradict the conclusion.
Skill tested: Necessary Assumption · how this choice captures the argument's function is the move to repeat next time.
83%
Out of Scope: other methods7% picked this
mulch containing paper and manure works better than methods of preventing soil erosion that do
The conclusion isn't saying that farmers would be better off with this manure/paper mixture than they would with any other method of preventing soil erosion. It's only claiming that the manure/paper mixture is better than paper alone or manure alone, so the author isn't making any assumptions about any other methods besides the three options being compared in the conclusion.
7%
Weakens2% picked this
mulch of pure manure provides nutrients to the soil that paper
The author would not want to provide evidence of this, since this would directly weaken her conclusion. This makes it sound like manure-alone might be better than a manure/paper mix.
2%

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