The ancient Romans understood the principles of water power very well, and in some outlying parts of their empire they made extensive and excellent use of water as an energy source. This makes it all the more striking that the Romans made do without water power in regions dominated by large cities.
Which one of the following, if true, contributes most to an explanation of the difference described above in the Romans’ use of water power?
The ancient Romans were adept at constructing and maintaining aqueducts that could carry quantities of water sufficient to supply large cities over considerable distances.
In the areas in which water power was not used, water flow in rivers and streams was substantial throughout the year but nevertheless exhibited some seasonal variation.
Water power was relatively vulnerable to sabotage, but any damage could be quickly and inexpensively repaired.
In most areas to which the use of water power was not extended, other, more traditional sources of energy continued to be used.
In heavily populated areas the introduction of water power would have been certain to cause social unrest by depriving large numbers of people of their livelihood.
Explanation for Question 9
This question asks you to identify the response that does most to explain an apparent discrepancy presented in the passage. The first step, then, is to determine what this discrepancy is. The passage notes the Romans’ extensive use of water power in some outlying parts of their empire, but in regions dominated by large cities, it says, they did without water power. Given the benefits of water power, an adequate response must help answer the question of why ancient Romans did not use water power in regions dominated by large cities when they had a demonstrated ability to do so.
Response (E) helps to answer that question. It presents an undesirable consequence that would have followed from the use of water power in heavily populated regions: social unrest due to significant loss of livelihood. By doing this, (E) identifies a negative aspect of water power use in heavily populated areas, and that gives a reason not to use it in regions dominated by large cities. Thus, (E) is the correct response.
Response (A) is incorrect. Rather than explaining the puzzling situation, it merely describes the ancient Romans’ ability to supply water over distances. If this has any bearing at all on the issue of water power, it would be to remove one possible impediment to the use of water power in regions dominated by large cities; it would not give a reason that the Romans did without it in those regions.
Response (B) is incorrect. While it speaks of the areas where water power was not used, which would include the regions dominated by large cities, it indicates the natural water supply in those areas was substantial although seasonally variable. This gives a reason to expect the use of water power in regions dominated by large cities, not a reason the Romans did without it in those regions.
Response (C) is incorrect. By noting that water power was relatively vulnerable to sabotage, (C) presents a possible reason to avoid the use of water power in important regions, but (C) also undermines that possible reason by describing how easily any damage could be repaired. So (C) does nothing to explain the puzzling situation.
Response (D) indicates that “more traditional” energy sources were used in areas without water power, which would include the regions dominated by large cities. This may help explain how these regions got along without water power—the use of traditional sources prevented them from being entirely without energy—but it adds little to our overall understanding, since we could already presume that these regions had energy sources. The fact that traditional sources of energy were employed in these regions does not explain why water power was not employed there, and that question would have to be addressed in order to explain the discrepancy in the Romans’ use of water power. Response (D) is thus incorrect.
This was a difficult question, based on the number of test takers who answered it correctly when it appeared on the LSAT.