Logical reasoning PrepTest 103 · Section 2 · Question 6

Incorrect. The stimulus doesn't discuss erosion, so this answer choice is out of scope.

Incorrect. While the thickness of Mars' crust is said to be related to why it can support such massive mountains, that doesn't mean there's a direct relationship between the tallest mountains and the thickest crust. Maybe the crust allows a mountain of a certain height to be formed, but there's some other factor that determines the actual height of the mountain that forms there.

Incorrect. We know only about a single mountain on Mars, so we can't make any determination about the average on Mars or Earth. It's possible that this mountain on Mars is the only mountain on Mars that's taller than 5 ft, and so the average on Earth ends up much higher, even though it can't support mountains as large as Mars in theory.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Valid

Question Type:
Must Be True

Stimulus Summary:
Mars - Largest volcano is 27km and the size of Romania

Earth - Crust is the same composition of Mars, but much thinner and would buckle under the mountain, so even at Mars gravity it couldn't support that big of a mountain

Answer Anticipation:
First, let's address a bit of a wrinkle here—there is an argument in our Must Be True question! That's relatively rare, but it doesn't change things—we should still treat each statement as true.

So with that said, what should we focus on? This stimulus focuses on a comparison between Earth and Mars, so the correct answer will likely reflect a point of comparison. Here, it's noted that they're similar in one way—the composition of the crust is "essentially the same." However, there's also a difference—the Earth's crust is "too thin" to support a mountain that exists on Mars. The correct answer will likely reflect one of these points of comparison.

One more note—see that the entire comparison is based on a hypothetical—"[e]ven if" Earth's gravity were the same as Mars. That's a wrinkle that we should have in mind as we look at answers, even if we're uncertain how it may change an answer up.

Answer Explanation:
The stimulus notes that even with gravity equal, the Earth's crust is too thin to support a mountain even close to the one on Mars. So it must be the case that, at least under this mountain on Mars, the Martian crust is thicker than the Earth's crust. This answer plays off of the comparison made in the stimulus.

Key Takeaway:
Comparisons are key types of statements in Must Be True questions that frequently lead to correct answers. Be on the lookout for them in this question type!

Incorrect. It's rare that a hypothetical ("if the Earth's crust were thicker) is a correct answer in a Must Be True question. The exception—when there's a hypothetical in the stimulus, which we have here ("Even if . . . "). However, that hypothetical is about gravity, and this answer is about crust thickness, so this answer is incorrect.