PrepTest 117, Section 2, Question 8
Most plants have developed chemical defenses against parasites.(41 more words not shown)
Each of the following, if(5 more words not shown)
- AHumans have been(14 more words not shown)
- BThe concentrations of(18 more words not shown)
- CNatural plant pesticides(12 more words not shown)
- DNatural plant pesticides(20 more words not shown)
- EThe synthetic pesticides(21 more words not shown)
Reading the argument
Being able to eat a plant's own chemicals doesn't mean we can safely eat whatever we spray onto it. Let's accept that people ingest natural pesticides without harm. A chemical can hurt a particular parasite without hurting us. That doesn't make 'pesticide' a guarantee of safety for humans—or of danger. We need to know whether the natural and synthetic chemicals are similar in the ways that matter here.
What if we've had time to adapt to the natural chemicals but not to the added ones? Then tolerating the natural pesticides wouldn't settle the risk from the synthetic ones. That's the gap I'd want to attack: the author moves between two groups without showing that the same safety conclusion applies to both.
What we’re looking for
This is a weaken-EXCEPT question. Four choices should give us a reason to doubt the comparison; we want the one that does not. Keep asking whether each answer creates a relevant difference between the natural pesticides and the synthetic pesticides.
Working the answers
- A
This weakens the argument. Long exposure and adaptation could explain why humans tolerate natural pesticides. That gives us a reason not to assume the same tolerance for synthetic pesticides. A doesn't explicitly prove that humans have no adaptation to any synthetic chemical; it exposes a possible reason the natural chemicals are harmless that hasn't been established for the added ones.
- B
This also weakens. Even if two chemicals had similar effects in small amounts, taking in much more of one could pose a different risk. B says the synthetic chemicals typically occur at higher concentrations in sprayed crops. The author can't rely on tolerating the lower concentrations to dismiss the additional threat.
- C
Potency gives us another relevant difference. A smaller amount of a more potent chemical may have a stronger effect than the same amount of a less potent one. C says synthetic pesticides are typically more potent, so the natural pesticides' harmlessness is a weaker basis for judging them safe.
- D
This weakens by distinguishing what the pesticides harm. A natural chemical might affect a particular parasite, while a synthetic pesticide harms a much wider range of organisms. That doesn't prove humans are among the organisms harmed, but it gives us another reason not to transfer the natural pesticide's safety to the synthetic one.
- ECorrect
Similar chemical structures point toward similarity between the two groups, rather than supplying the relevant difference the other answers give us. That doesn't prove identical effects or establish that synthetic pesticides are safe. It simply doesn't challenge the author's comparison in the way A through D do. Since we're looking for the exception to weakening, E is the answer.
More Weaken questions
Learn the LSAT our way
Our platform drills Weaken questions at your level and adjusts as you improve.