Logical reasoning PrepTest 122 · Section 2 · Question 20

Incorrect. There's no discussion of recycling in the stimulus, so this answer is out of scope.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Valid (Assuming lead and mercury are dangerous. They are.)

Question Type:
Must Be True

Stimulus Summary:
Conclusion - Discarding old appliances can be dangerous
Why? - They have heavy metals in them, and:
(1) If landfills are operated properly, then disposing of appliances there poses no risk
(2) If landfills aren't, then disposing of appliances there can leak heavy metals into the groundwater
(3) If these appliances are incinerated, the heavy metals get into the air

Answer Anticipation:
Unlike most Must Be True questions, this stimulus features an argument. And unlike most questions with arguments, we should treat each statement as true instead of wondering about the logic of the argument (and this argument is valid, anyway).

Instead, we need to find an answer supported by the stimulus. It's difficult to anticipate an answer since the argument doesn't have conditionals that build together. It does have causal statements, but those causal statements don't build with others to form a chain or an inference.

We're left with our understanding of the situation, and hopefully enough time to analyze the answers!

Answer Explanation:
When trash is incinerated, the heavy metals escape into the air. This is dangerous. Ergo, it's supported that this shouldn't be done. Normally, we wouldn't select an answer talking about what "should" be done in a Must Be True question without similar language in the stimulus, but we can infer that something that is dangerous shouldn't be done, so we can select this answer.

Key Takeaway:
Don't get wrapped up in the logic of a Must Be True question with an argument in it, wondering if it's valid or not. Treat it the same as all other Must Be True questions—each statement is true, and they support one (and only one) answer.

Incorrect. We can infer that chlorofluorocarbons are dangerous, but not specifically how they're dangerous. Therefore, we can't select this answer stating that they're dangerous because they harm the atmosphere. (They do, so this question might actually be harder if you know the science, as this answer is actually true!)

Incorrect. There's no comparison of appliances made in different time periods as being more or less dangerous. It notes that discarding "old" appliances can be dangerous because, presumably, no one is throwing out their new fridge!

Incorrect. If the landfill is properly managed, "such materials pose no threat," so there's no need to keep them out of all landfills.