Logical reasoning PrepTest 152 · Section 2 · Question 15

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Weaken

Stimulus Summary:
A bunch of gold artifacts had trace elements matching an ancient gold mine and no other known mine, so the artifacts' gold probably came from that mine.

Answer Anticipation:
This argument relies on that comparison of trace elements to establish that the gold in the artifacts came from the mine in question. Since the argument is based on that similarity, we can weaken it by finding another source that is also similar to the gold in question (note that the stimulus just says the gold doesn't match the gold from any known mine—there might be an unknown gold mine, or something other than a mine with matching gold), or by finding a relevant difference between the gold in the artifacts and the gold in the mine.

Answer Explanation:
This answer choice brings up another source for gold that would match that of the mine—nearby riverbeds. Since these riverbeds had gold from the same source, they should have the same trace elements, and thus the artifacts could have been made by people getting gold out of the riverbed. By suggesting another source that would have matching gold, this answer weakens the argument.

Key Takeaway:
Always consider alternatives. As soon as you read a conclusion like this, your first thought should be, "Well, where else could the gold have come from?" Even if you can't answer that question, having it in the back of your head would make it much easier to choose an answer choice that provides an answer to your question—just like answer choice (A) does here.

Incorrect. If anything, this supports the argument by connecting the mine to the artifacts.

Incorrect. What's relevant to a determination of whether the mine supplied the gold for the artifacts is when the mine was last operated. If it was last operated centuries before the artifacts were made, then it'd be less likely to have supplied that gold.

Incorrect. Great trap answer! It's trying to get you to think this is providing an alternative source for the gold in the artifacts. However, the gold in the earlier artifacts must have come from somewhere, and the trace elements match only this one mine. So the gold in the studied artifacts could have been from earlier artifacts, but the evidence still suggests the initial source of the gold was that ancient mine.

Incorrect. If anything, the dispersal of this gold throughout the world would suggest that it can serve as the source for a wider range of artifacts. That said, there's no discussion of where the studied artifacts came from, so this answer doesn't impact the argument.