Self-study
Farmer: Crops genetically engineered to produce toxins that enable them to resist insect pests do not need to be sprayed with insecticides. Since excessive spraying of insecticides has harmed wildlife populations near croplands, using such genetically engineered crops more widely is likely to help wildlife populations to recover.
26.
Which one of the following is an assumption the farmer's argument requires?
a
Use of the crops that have been genetically engineered to resist insect pests in place of crops that have been sprayed with insecticides will cause less harm to wildlife populations.
Without this assumption, the argument falls apart. The author concludes that switching to GE crops will help wildlife recover, but that conclusion depends on GE crops actually causing less total harm to wildlife than the current insecticide-sprayed crops.
You can confirm this with the negation test. Negate (A): using GE crops in place of insecticide-sprayed crops will not cause less harm to wildlife. If that's true, there's no reason to think GE crops would help wildlife recover. Replacing current crops with crops that cause just as much harm wouldn’t help recovery. So the author must assume that using the genetically engineered crops will cause less harm.
b
Wildlife populations that have been harmed by the excessive spraying of insecticides on croplands are likely to recover if the amount of insecticides sprayed on those croplands is reduced even slightly.
The word to focus on is
Current crops:
◼◼◼◼◼◼◼◼◼◼
← excessive
Slight reduction:
◼◼◼◼◼◼◼◼◼
← still excessive!
GE crops:
◼◼◼
✓ not excessive
The author doesn't need to assume that any reduction in spraying helps wildlife. The author just needs to assume that GE crops bring spraying below the "excessive" level. (B) is too extreme in saying wildlife would recover from "even a slight" reduction.
c
Crops that have been genetically engineered to resist insect pests are never sprayed with insecticides that harm wildlife populations.
Same keyword, same issue as (B). The stimulus says excessive spraying harms wildlife, not that any spraying harms wildlife. So the author doesn't need to assume GE crops are never sprayed. The author just needs to assume that any spraying that does happen isn't excessive enough to harm wildlife.
GE crops:
◼◼◼
✓ not excessive
"Never sprayed":
overkill — not required
Think of it this way: if GE crops get sprayed with a small, non-excessive amount of insecticide, the argument still works.
d
Use of crops that have been genetically engineered to resist insect pests is no more costly to farmers than the use of insecticides on crops that are not genetically engineered.
The argument's reasoning has nothing to do with cost to farmers. The author is making a claim about whether GE crops will help wildlife recover, not about whether farmers can afford them. Even if GE crops cost ten times more than insecticides, that wouldn't change whether they're better for wildlife.
e
If a wider use of certain crops that have been genetically engineered to resist insect pests is likely to help at least some wildlife populations to recover, it is likely to have that effect only because its use will prevent excessive and ineffective spraying of insecticides on croplands.
This says that if GE crops help wildlife, the only reason would be reduced insecticide spraying. But the author doesn't need that to be the only reason. If GE crops help wildlife for additional reasons beyond reduced spraying, that wouldn't undermine the author's conclusion. It would actually make the conclusion more likely to be true, not less. The argument just needs reduced spraying to be one path to helping wildlife, not the exclusive path.