Logical reasoning PrepTest 153 · Section 3 · Question 3

Incorrect. Not relevant to this issue. Nobody's proposing turning off the power. Rerouting power lines wouldn't necessarily cause power loss; even if it did, it might be justified if the high-tension lines are an even bigger threat. But that's all an argument for a different stimulus. Out of scope here.

Incorrect. We, too, can safely ignore economic realities, because they aren't part of the argument. The conclusion is based on safety alone.

Incorrect. Too broad. "Various modern practices" might include things like smoking cigarettes and eating too much red meat that have nothing to do with high-tension lines.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with Sufficient Premise

Stimulus Summary:
A columnist affirms that we have a civic duty to protect public health, but nevertheless they conclude we shouldn't bother to reroute high-tension power lines away from populous areas. That's because we should only devote resources to protecting the public against "well-substantiated" health risks.

Answer Anticipation:
To understand if the columnist's conclusion is valid or not, we need one key piece of information. Do high-tension power lines constitute a "well-substantiated threat to public health," or not? If they do, resources could potentially be used on protecting the public against them (but don't have to be, according to this reasoning). If not, resources must be used elsewhere. So, the correct answer should tell us that they're not a well-substantiated threat.

Answer Explanation:
Perfect! If we have no substantiation of a risk to public health from the power lines, then they can't possibly be a well-substantiated threat.

Key Takeaway:
Even in situations like this one where diagramming the whole stimulus isn't advisable, the presence of a conditional word like "only" should make you sit up and take notice. You might even want to diagram just that part. In this case, "IF devote resources, THEN well-substantiated threat to public health" would do it. Take the contrapositive and you'll find "IF NOT well-substantiated threat, then DO NOT devote resources." So, (D) is clearly correct.

Incorrect. Nice mad scientist reasoning, but irrelevant to whether or not they're already a proven public health threat. We just need to know if they are or aren't in that general category.