Because Texas usually loses 5 percent of its cotton crop to insects, this year farmers there started spraying the pesticide...

GMAT Critical Reasoning : (CR) Questions

Source: Mock

Critical Reasoning

Logically Completes

MEDIUM

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Notes

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Because Texas usually loses 5 percent of its cotton crop to insects, this year farmers there started spraying the pesticide malathion in order to eradicate the principal culprit, the boll weevil. Spraying killed 98 percent of boll weevils, but because malathion reduced populations of predators of the beet armyworm, that insect did more damage to the crop than the boll weevil ever has. Even so, the spraying program should not yet be halted, since ______________.

Which of the following most logically completes the argument?

a recovery of the boll weevil population would reduce the amount of food available to the beet armyworm

other regions that have successfully used malathion to reduce insect damage by eradicating boll weevils were not regions inhabited by the beet armyworm

the boll weevil population that survived the first year's spraying is small enough that, even if spraying of malathion discontinued, it will never return to the size it had before the program

malathion has no effect on the beet armyworms that are directly exposed to it

complete eradication of the boll weevil requires only one further year of spraying, after which the populations of predators of the beet armyworms will quickly recover

Solution

Passage Analysis:

Text from Passage	Analysis
Because Texas usually loses \(5\%\) of its cotton crop to insects, this year farmers there started spraying the pesticide malathion in order to eradicate the principal culprit, the boll weevil.	What it says: Texas normally loses \(5\%\) of cotton to bugs, so farmers decided to spray malathion to kill boll weevils (the main problem bug) What it does: Sets up the background problem and introduces the solution farmers tried What it is: Author's factual setup Visualization: Normal year: \(100\) cotton units \(\rightarrow\) lose \(5\) units to insects (mostly boll weevils)
Spraying killed \(98\%\) of boll weevils, but because malathion reduced populations of predators of the beet armyworm, that insect did more damage to the crop than the boll weevil ever has.	What it says: The spray worked great on boll weevils (killed \(98\%\)) but accidentally killed the bugs that eat beet armyworms, so now beet armyworms are doing even worse damage What it does: Shows the solution had an unintended consequence that made things worse overall What it is: Author's explanation of unexpected results Visualization: Boll weevils: \(100 \rightarrow 2\) remaining (success!) Predator bugs: many \(\rightarrow\) few (oops!) Beet armyworms: some \(\rightarrow\) LOTS (bigger problem than before)
Even so, the spraying program should not yet be halted, since ______.	What it says: Despite the bad results, we shouldn't stop spraying yet because... (blank to fill) What it does: Makes a surprising conclusion that goes against what we'd expect and asks us to find the reason What it is: Author's conclusion with missing premise

Argument Flow:

We start with a problem (crop loss to insects), then see a solution attempt (spraying) that technically worked but created a bigger problem (worse overall damage). Despite this seeming failure, the author argues we should continue the program.

Main Conclusion:

The spraying program should not be stopped yet, even though it caused more crop damage than before.

Logical Structure:

This is an incomplete argument where we need to find the missing premise that would logically support continuing a program that appears to have backfired. The structure is: Problem \(\rightarrow\) Solution \(\rightarrow\) Unexpected bad results \(\rightarrow\) Continue anyway because [missing reason].

Prethinking:

Question type:

Logically Completes - We need to find a reason that supports continuing the spraying program despite the fact that beet armyworms are now causing more damage than boll weevils ever did.

Precision of Claims

The argument involves specific quantitative claims (\(5\%\) crop loss, \(98\%\) boll weevil kill rate) and a qualitative comparison (beet armyworm damage is worse than boll weevil damage ever was). The conclusion specifically states the program should 'not yet' be halted, suggesting a temporal element.

Strategy

Since this is a 'Logically Completes' question, we need to find scenarios that provide logical justification for the surprising conclusion that spraying should continue despite apparently making things worse. The key insight is that the conclusion says 'not yet' - implying there might be future benefits or the current situation might be temporary. We should look for reasons that either:

explain why the current bad situation is temporary/fixable
suggest long-term benefits outweigh short-term costs
indicate the situation will improve with continued spraying

Answer Choices Explained

a recovery of the boll weevil population would reduce the amount of food available to the beet armyworm

This suggests that if boll weevils recover, they would compete with beet armyworms for food, potentially reducing armyworm damage. However, this doesn't provide a strong reason to continue spraying since we're trying to eradicate boll weevils, not encourage their recovery. This logic would actually support stopping the spraying program to let boll weevils recover and compete with armyworms.

other regions that have successfully used malathion to reduce insect damage by eradicating boll weevils were not regions inhabited by the beet armyworm

This tells us that other successful regions didn't have beet armyworms, which explains why malathion worked there but not in Texas. While this explains the difference in outcomes, it doesn't give us any reason why Texas should continue the spraying program. If anything, this suggests the program won't work in Texas due to the beet armyworm problem.

the boll weevil population that survived the first year's spraying is small enough that, even if spraying of malathion discontinued, it will never return to the size it had before the program

This states that the remaining boll weevil population is so small it won't recover even if spraying stops. While this might seem positive, it doesn't address the current beet armyworm problem that's causing more damage than boll weevils ever did. There's no reason provided to continue spraying if boll weevils won't be a problem anyway.

malathion has no effect on the beet armyworms that are directly exposed to it

Saying malathion doesn't directly affect beet armyworms explains why they're not being killed by the pesticide, but this doesn't provide justification for continuing the program. If malathion can't kill the insects that are now the bigger problem, this would actually be a reason to stop spraying.

complete eradication of the boll weevil requires only one further year of spraying, after which the populations of predators of the beet armyworms will quickly recover

This provides the perfect justification for continuing the program. It tells us that complete boll weevil eradication needs just one more year of spraying, and crucially, after that the predator populations will recover quickly. This means the beet armyworm problem is temporary - once predators recover, they'll control the armyworms again. The program should continue because we're close to solving both problems permanently.

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