Necessary AssumptionDiff: Easy
Logic Breakdown
Passage Summary: Scientists spent years looking for a bug to kill a pest they misidentified. Because the pest is a different species than they thought, they assume all their work was useless.
Conclusion: The time spent looking for a parasite to control the whitefly pest was a total waste.
Reasoning: The researchers looked for parasites that target sweet-potato whiteflies, but the pest was recently discovered to be a different species, the silverleaf whitefly.
Analysis: The argument relies on a significant 'Gap' between the identity of the pest and the effectiveness of the parasite. It assumes that a parasite for one species (sweet-potato whitefly) cannot possibly be effective against a different species (silverleaf whitefly). If there were any overlap in the parasites' targets, the effort wouldn't be 'wasted.' Look for an answer that establishes this strict species-specificity as a necessary condition for the conclusion to hold.
Conclusion: The time spent looking for a parasite to control the whitefly pest was a total waste.
Reasoning: The researchers looked for parasites that target sweet-potato whiteflies, but the pest was recently discovered to be a different species, the silverleaf whitefly.
Analysis: The argument relies on a significant 'Gap' between the identity of the pest and the effectiveness of the parasite. It assumes that a parasite for one species (sweet-potato whitefly) cannot possibly be effective against a different species (silverleaf whitefly). If there were any overlap in the parasites' targets, the effort wouldn't be 'wasted.' Look for an answer that establishes this strict species-specificity as a necessary condition for the conclusion to hold.
Passage Stimulus
Passage Redacted
Unlock Full Passage2.Which one of the following is an assumption on which the argument relies?
Correct Answer
D
D states the crucial assumption: no parasite of the sweet-potato whitefly is also a parasite of the silverleaf whitefly. Negation test: suppose some are shared—then the prior search could have identified a useful parasite, contradicting the “wasted effort” conclusion. So D is necessary.
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