Logical reasoning PrepTest 120 · Section 4 · Question 5

Incorrect. The conclusion is about the sickles already found at the first site, so other sickles—even undiscovered ones at the first site—are out of scope.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Weaken

Stimulus Summary:
Site 1 - Sickles have scratches
Site 2 - Sickles didn't have scratches
Sickles get scratched when used to harvest grain
Explanation/Conclusion - Site 1 sickles harvested grain; Site 2 sickles didn't

Answer Anticipation:
This argument falls into a common pattern on the LSAT—a Phenomenon/Explanation argument. It's noted that the sickles at one site are scratched, and at another they're not. From this, and from the premise that harvesting grain with a sickle scratches it, the argument reaches an explanation—Site 1 sickles were used to harvest grain, but Site 2 sickles weren't.

Whenever we're dealing with a Phenomenon/Explanation argument, we should start by thinking about alternative explanations. For this one, we should focus on the sickles found at Site 1. Why? Because it's established that a sickle used to harvest grain would be scratched, and the Site 2 sickles aren't. That's definitive proof that they weren't used to harvest grain, so we can't undermine it!

So let's focus on Site 1. It's certainly been established that the scratches could have been the result of harvesting grain, but there's nothing saying that other uses can't cause scratches. If something else could have caused the scratches, then the argument that these sickles were used to harvest grain would be weakened. Let's look for an answer providing evidence of that.

Answer Explanation:
This answer straight up says that the scratches on the Site 1 sickles were caused by something other than harvesting grain. Without those scratches being the result of grain harvesting, there's nothing to prove that they were used for that purpose, so this answer completely undermines the argument.

Key Takeaway:
First, always consider alternative explanations when you're dealing with a Phenomenon/Explanation passage. Second, if there's a two-part conclusion (e.g., here, talking about Site 1 sickles and Site 2 sickles), check each part individually for assumptions. Sometimes, as in here, you can focus on just one of the two conclusions!

Incorrect. This answer doesn't establish that these ritual uses resulted in scratches to the blades. As such, it doesn't suggest an alternative explanation that definitely accounts for the scratches. And, in fact, there's evidence that these uses didn't result in scratches, since the sickles at Site 2 were used for this purpose but didn't have scratches.

Incorrect. If anything, this suggests that the Site 2 sickles weren't used for grain harvesting, but that lines up with the argument.

Incorrect. Who made them is immaterial to whether the scratches indicate use for wheat harvesting.