PrepTest 103, Section 2, Question 6
The largest volcano on Mars rises 27 kilometers(72 more words not shown)
If the statements above are(15 more words not shown)
- AThe surface of(15 more words not shown)
- BThe highest volcanoes(8 more words not shown)
- COn average, volcanoes(8 more words not shown)
- DThe crust of(17 more words not shown)
- EAt least some(20 more words not shown)
Reading the argument
How is Mars holding up that enormous volcano if Earth's crust could not?
The passage rules out two easy answers. The crusts have essentially the same composition, so we cannot simply say Mars uses a stronger material. And even lowering Earth's gravity to match Mars would not solve the problem. Earth's crust would still be too thin and would buckle under the weight.
That points us toward thickness. Mars is supporting the volcano; Earth could not support a mass like it because its crust is too thin. The connection is that Mars must have thicker crust at least somewhere. We do not need to make the same claim about every point on either planet.
What we’re looking for
The question asks what must follow from the passage. That limited thickness comparison is my prediction. Stay with the feature the explanation actually identifies.
Working the answers
- A
Erosion is not discussed. Nothing tells us how strongly wind, water, or other erosive forces affect either surface. The given comparison concerns the crust's ability to support a huge mass, not how quickly the surface wears away.
- B
Thick enough is not the same as thickest. The largest volcano needs support, but the very thickest part of Mars's crust could lie under a flat plain. We have no ranking that matches each volcano's height with the thickness beneath it. B adds that relationship.
- C
One enormous volcano does not establish an average. Mars could have this giant and many very small volcanoes. Without information about the rest, we cannot compare the planets' average volcanic heights.
- DCorrect
The passage attributes Earth's inability to support a volcano of this size to the thinness of its crust, even after accounting for gravity and comparable composition. Mars does support such a volcano. The supported comparison is that at least some of its crust is thicker than Earth's.
The qualification matters: D does not claim that Mars has thicker crust everywhere, or that every Martian volcano is larger.
- E
A thicker crust could remove a limit on what a volcano can weigh. That does not establish that any existing volcano would actually grow larger if the limit were removed. Other things could determine its size. The passage tells us why Earth cannot support the Martian giant; it does not predict how Earth's volcanoes would change under different conditions.
More Must Be True questions
Learn the LSAT our way
Our platform drills Must Be True questions at your level and adjusts as you improve.