PrepTest 106, Section 1, Question 12
People who say that Dooney County is flat(40 more words not shown)
The author's conclusion in the(6 more words not shown)
- Athe only cause(5 more words not shown)
- Bthere are terraces(12 more words not shown)
- Cterraces of the(14 more words not shown)
- Don flat land(5 more words not shown)
- Ethe only terraces(6 more words not shown)
Reading the argument
How reliable is that report about the terraces? My first reaction is to check what the author has heard. If the report were mistaken, the evidence for the county's being uneven would disappear. Rather than treating “I hear” as automatically reliable or unreliable, we should notice how much the argument asks that report to do.
The conclusion comes first: people calling Dooney County flat are wrong. The author then gives a rule about flat farmland. Farmers on that land don't build terraces to prevent erosion, because water erosion isn't a problem there. Finally, the author points to the reported terraces as a reason to reject the description of the county as flat.
What we’re looking for
We're asked for an assumption this reasoning needs. My initial thought is that the report needs to be accurate. But let's inspect what connects the reported terraces to the rule about flat land. We need something the argument relies on, not every additional fact we could learn about erosion or farming.
Working the answers
- A
The argument doesn't require water to be the only cause of soil erosion. Wind or some other cause could exist without changing the stated rule about what farmers on flat land do. The author needs a connection between these terraces and the reasoning offered, not a complete account of every kind of erosion.
- BCorrect
This identifies a gap beyond the report's accuracy: why were the terraces built? The rule concerns terraces built to prevent erosion. The report merely says there are terraces.
What if every reported terrace was a landscaping feature, built because someone liked how it looked? The terraces could exist exactly as reported without being the erosion-prevention terraces described in the premise. Their presence would then fail to support the intended inference.
B connects at least some actual terraces to that purpose. It doesn't need every terrace in the county to have been built for erosion prevention; it needs an instance that makes the author's rule relevant to the land being discussed.
- C
Intended purpose and demonstrated effectiveness are different. A farmer could build a terrace to prevent erosion even if it were poorly designed and didn't work. Conversely, a terrace might prevent erosion despite having been built for appearance. The argument's rule concerns what farmers build to accomplish a purpose, not whether the resulting structures have been proved effective.
- D
The passage says water erosion isn't a problem on flat land. D rules out all soil erosion there, a broader claim the argument doesn't need. Even if another process eroded flat land, we would still need to know why these particular terraces were built.
- E
Terraces could also exist at a home, a castle, or some other site outside farmland. The author uses the reported farm terraces as evidence. That doesn't depend on proving there are no terraces anywhere else in the county.
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