PT13.S4.Q5

PrepTest 13 - Section 4 - Question 5

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Planetary bodies differ from one another in their composition, but most of those in the Solar System have solid surfaces. ██████ ███ ████ ██ ████ █ █████████ ████ █████████ ██████ ████ ██ █████ ████████ ███████ ███ ███████ ██ ███ ████ ████ ███ ██ ███████ ███ ████████ ██ ██████ ███ █████████ ████ ████ █ █████ ███████ █████ ███████ ██ ███ ███████ ███ ████████ ██ █████ ███████ ███████ ██████████ ██ █████████ ████████ ████ ████ ███ █████████ █████ ████ ███ █████████ ██████ ██ ███ █████ ███████ ████ ██ ███████ █ ████ ████ ████ █████████ ██ ████████ ████ █████ ███ ████████ ████ ████ ███ █████████ ████████

Stimulus Breakdown

The stimulus throws a bunch of information at us about the surfaces of planetary bodies. These are conditional claims, so we can organize them by diagramming before we start looking for our must-be-true answer. We can also kick up the idea of "planetary bodies with solid surfaces" to the domain to simplify things.

1: /core generates enough heat for volcanic action → /surface renewed
2: /surface renewed → lots of craters
3: Earth's Moon/surface renewed AND Earth's Moonlots of craters
4: solid icy surface ←some→ /lots of craters
5: Europavery cold moon AND Europasolid icy surface AND Europa/lots of craters

We can also make a few up-front inferences that might help us find the correct answer. We can start by chaining together claims 1 and 2 and then see how that connects with some other claims.

1 + 2: /core generates enough heat for volcanic action → /surface renewed → lots of craters
contrapositive: /lots of craters → surface renewed → core generates enough heat for volcanic action
1 + 2 + 4: solid icy surface ←some→ core generates enough heat for volcanic action
1 + 2 + 5: Europacore generates enough heat for volcanic action

Answer Choice Strategy

Although our list of inferences is not exhaustive, it still gives us enough to hunt for an answer. Each inference we identified must be true, so an answer choice that reflects one of them would be correct. If we don't find an answer we've predicted, we can revert to process of elimination. Above all, because this is a fairly complex stimulus, it's useful to link answer choices back to the stimulus. That will let us be more certain if they really must be true.

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5.

If the claims above are █████ █████ ███ ██ ███ █████████ █████ ██ ███ █████ ██ █████ ██ █████

a

The Earth’s Moon ████ ███ ████ ██ ███ ████████

All we know about Earth's Moon is that its surface has not been renewed, and that it has lots of craters. We also know that there are some planetary bodies with icy surfaces and few craters, but it doesn't follow that the Moon must not be icy because it's got craters.

4%
b

If a planetary ████ ████ ███ ████ █ ███████ ██████████ ████████ ███ ████ ████ ███ ████████ ██████ ████ ██ █████ ████████ ███████

The stimulus tells us that a core generating heat is necessary to renew a body's surface, which in turn is necessary to avoid pockmarking. This lets us infer the opposite claim: if a body is not pockmarked, its core must generate enough heat for volcanic action.

12%
c

Some planetary bodies █████ █████ ████████ ██████ ████ ██ █████ ████████ ██████ ██ ███ ████ █████ ███ █████████

The only planetary body the stimulus mentions whose core generates enough heat for volcanic action is Europa—we know this because its surface has few craters, which is sufficient to know its core generates enough heat. But Europa does have a solid icy surface; we don't know of any hot-core bodies that don't.

13%
d

Some of Jupiter’s █████ ███ ███████ ██████████ ██ █████████ ████████

Europa is the only moon of Jupiter we know about, and it is not pockmarked. We don't know of any moons of Jupiter that are pockmarked.

2%
e

Some very cold █████████ ██████ ████ █████ ████ ████████ ██████ ████ ██ █████ ████████ ███████

Europa is a very cold body with few craters. Because it has few craters, we can infer that its surface must have been renewed, which means its core must generate enough heat. And that's enough for this to be true of "some" very cold bodies.

68%

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