Logical reasoning PrepTest 142 · Section 2 · Question 14

Incorrect. First, the relevant age is of the marks, not the sandstone. For all we know, the marks were made millions of years after the sandstone formed. Second, even if we're not precise, the timeline discussed is half a billion years. We can be off by a few millions and still be much earlier than any known multicellular life.

Incorrect. This answer establishes that geological processes could have left the marks, aligning with the argument.

Incorrect. The stimulus established that the earliest known traces of multicellular life are from 500 million years after these marks were left, and this answer doesn't overcome that obstacle to promoting multicellular life as a potential alternative cause.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Weaken

Stimulus Summary:
Discovery—Marks that look like worm tracks in sandstone
Background—They were made over 500m years before the earliest known multicellular life
Conclusion—They were probably made by geological processes

Answer Anticipation:
This argument brings up an observed phenomenon—marks in old sandstone—and then concludes a probable explanation for that phenomenon—geological processes. Whenever an argument concludes an explanation for a phenomenon, you should start thinking about alternative explanations.

However, there's a wrinkle here—the conclusion is that the marks were "probably" made by geological processes. Alternative causes that are potential but not probable are actually included in that conclusion—for instance, it's possible that aliens left those marks, but that's such a remote possibility that it doesn't really affect the conclusion. Because of this, the correct answer will have to bring up another possibility that itself seems probable. Or it could go another route that is less frequent seen in a phenomenon/explanation argument—a direct attack on the given explanation.

Answer Explanation:
This answer directly attacks the explanation provided in the conclusion, and it does so with enough force to call the probability of that explanation into question. If geological processes that are "likely" to have caused these tracks couldn't have happened at the time and place where these marks were left, then it's not likely that the marks were caused by geological processes, and the conclusion is directly undermined.

Key Takeaway:
In general, when an actument reaches a conclusion that's an explanation for an observed phenomenon, answers deal with alternative explanations in some way. However, when the argument concludes only a probability of that, the correct answer needs to carry more weight in bringing up an alternative, or it'll go another route—a direct attack on the explanation provided.

Incorrect. This answer doesn't change our timeline—the earliest traces of multicellular life are still from half a billion years after the marks were left. While the evidence might be scarce, it's still from much later than the marks were left. In order to undermine the argument, this answer would need to establish a probability that worms were around at the time the marks were left and were more likely to be the source than geological processes, and this answer establishes neither of those as true.