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  3. Parland’s alligator population has been declining in recent years, primarily because of hunting. Alligators prey heavily on a sp

Parland’s alligator population has been declining in recent years, primarily because of hunting. Alligators prey heavily on a sp

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问题 Parland’s alligator population has been declining in recent years, primarily because of hunting. Alligators prey heavily on a species of freshwater fish that is highly valued as food by Parlanders, who had hoped that the decline in the alligator population would lead to an increase in the numbers of these fish available for human consumption. Yet the population of this fish species has also declined, even though the annual number caught for human consumption has not increased.
Which of the following, if true, most helps to explain the decline in the population of the fish species?
选项 A、The decline in the alligator population has meant that fishers can work in some parts of lakes and rivers that were formerly too dangerous.
B、Over the last few years, Parland’s commercial fishing enterprises have increased the number of fishing boats they use.
C、Many Parlanders who hunt alligators do so because of the high market price of alligator skins, not because of the threat alligators pose to the fish population.
D、During Parland’s dry season, holes dug by alligators remain filled with water long enough to provide a safe place for the eggs of this fish species to hatch.
E、In several neighboring countries through which Parland’s rivers also flow, alligators are at risk of extinction as a result of extensive hunting.
答案D
解析 Argument Construction
Situation The alligators in a certain region prey heavily on a certain species of fish that is prized for human consumption. However, although in recent years hunting has reduced the population of alligaters in the region, the population of the prized freshwater fish species has declined. The annual number caught for human consumption has not increased.
Reasoning What might explain the decline in the population of the prized fish species, despite both the decrease in population of another species that preys heavily on the prized fish and the lack of increase in fishing for the species for human consumption?’The population of the fish species declined, despite both the presence of a factor that we might be expected to produce an increase in the population of the species and the absence of a factor that we might ordinarily expect to explain the decrease. This situation may seem puzzling, and we may thus wish to find an explanation for it.
A Given that fishers can work in parts of lakes and rivers that were formerly too dangerous to work in, we might expect fishing of the prized species to increase and thus expect the population of the species to decrease. Although this might explain a decrease in the population of the fish species if fishing for the species increased, we have been given reason to believe that fishing for the species decreased.
B As with option A, the statement in this option suggests that fishing in the region may have increased and thus that fishing for the prized fish species for human consumption may have increased. This might explain the decrease in the population of the fish species if the statement were correct. However, we have been given that fishing for the prized fish species for human consumption has decreased.
C The statement in this option provides an explanation of why the alligator hunting has occurred. Given that the alligators prey on the fish, this might help to explain an increase in the population of the prized fish species, had such an increase occurred. However, we are given that the population of the fish species in the region has decreased.
D Correct. Despite the fact that alligators prey on the prized fish species, this statement describes a way in which the fish species may be dependent on the alligators, in such a way that a decline in the population of the alligators could contribute to a decline in the fish species.
E The statement in this option serves to amplify a point that is given in the puzzling situation of a decline in the population of the fish species despite (among other factors) a decrease in the population of the alligators. It does not explain why a decline in the population of the alligator species may have contributed to a decline in the population of the fish species.
The correct answer is D.
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