PrepTest 155, Section 2, Question 6
Saturn’s moon Enceladus has a rocky core and(50 more words not shown)
Which one of the following(10 more words not shown)
- ASaturn’s moon Enceladus(8 more words not shown)
- BThere must be(15 more words not shown)
- CThe Cassini space(9 more words not shown)
- DDensity measurements reveal(11 more words not shown)
- EAnything denser than(14 more words not shown)
Reading the argument
Why does there have to be water between the rock and the ice? That's my first reaction to the second sentence. The author then gives us the reason: the probe detected something denser than ice in that space. Could it be some other material? Before pressing that objection, notice the final statement. The argument explicitly tells us that what was detected could only be liquid water. If we accept that premise, suggesting another material just fights the information we're given.
We could also wonder whether the probe's measurements were accurate. But the question doesn't ask us to undermine the scientific finding. It asks what conclusion the author draws from it.
What we’re looking for
Follow where the evidence leads. The rocky core and icy surface establish the setting. The density measurement identifies something between them, and the final statement identifies that material as water. Together, those reasons support the second sentence: there must be a lake of liquid water between the two layers. That's the overall conclusion, even though it appears before most of its support.
Working the answers
- A
This is the background: the moon has a rocky core and an icy surface. The author isn't using the measurements to persuade us that these layers exist. The argument uses those layers to locate the lake it claims must lie between them.
- BCorrect
The lake of liquid water is what the author is trying to establish. Ask why we should believe it is there, and the following sentences supply the answer: the density readings detected something in that space, and the material detected could only be water.
- C
This describes how the information was obtained. Using a probe to measure density matters because of what its findings tell us about the material between the layers. The measurement procedure supports the conclusion about the lake; it isn't the main claim being defended.
- D
This is the finding from the probe. It still leaves us asking what the denser material is. The argument takes the next step by identifying it as water and concluding that a lake exists. D stops at the evidence rather than its ultimate point.
- E
This supplies the connection between the density finding and the water conclusion. Combined with the discovery of denser material in that space, it supports the existence of a lake. But the overall conclusion concerns what actually exists inside Enceladus, not just what a material with these characteristics would have to be.
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