Logical reasoning PrepTest 117 · Section 2 · Question 8

Incorrect. While this answer doesn't specifically mention synthetic pesticides, it brings up something true of organic pesticides that can't be true of synthetic ones (humans haven't had that technology for millennia). Since this difference has to do with safety in human consumption, it weakens the argument and thus can be eliminated.

Incorrect. This answer highlights a difference, and the amount of a substance consumed is definitely related to how safe it is to consume, so this answer weakens the argument.

Incorrect. Another relevant difference, so this also weakens the argument.

Incorrect. One more difference. This one is relevant, as well. If natural pesticides are targeted at specific parasites but synthetic ones affect more organisms, the latter are more likely to harm humans. This, therefore, weakens the argument.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Bizarro Weaken

Stimulus Summary:
Plants have natural pesticides that humans safely eat every day, so synthetic pesticides are also safe for humans.

Answer Anticipation:
While correlation/causation flaws are the most common in Weaken questions, this one doesn't have such a flaw—instead, it has another common flaw in this question type that similarly has patterns of what to look for in the answer choices.

Here, the argument shows that natural pesticides are safe, and then concludes that synthetic pesticides are safe. That's a jump between two distinct things, and, as such, it's assuming that natural and synthetic pesticides are similar as far as safety for humans is concerned.

That similarity, however, is never established. Since this argument is relying on them being similar to work, relevant differences will weaken it. Let's head into the answer choices and eliminate any that bring up a relevant difference between natural and synthetic pesticides.

Answer Explanation:
First, without a degree in chemistry, we can't say that structure is related to toxicity. Ignoring that, though, this answer brings up a similarity, not a difference, so if it is relevant, it strengthens the argument. Since either way it doesn't weaken the argument, this is the correct answer.

Key Takeaway:
When an argument relies on two things being similar, you can weaken it with a relevant difference. When an argument relies on two things being different, you can weaken it with a relevant similarity.