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标题: GWD-TN 第24套 Q18 没找到讨论的 [打印本页]

作者: 224zy    时间: 2011-9-23 00:48
标题: GWD-TN 第24套 Q18 没找到讨论的
这道题没看懂,麻烦NN帮忙解释下

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?
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.

答案选D。 我选了B。 没懂什么意思。
谢谢
作者: cdwayne    时间: 2011-9-24 08:40
因為獵捕鱷魚數量減少,預期鱷魚的食物(某魚)會變多,結果卻跟預期相反。請說明原因。

(D) 鱷魚挖的洞可以讓某魚產卵。(所以鱷魚變少魚就跟著變少了)

(B) 加深矛盾,增加漁船結果總漁獲量不變豈不暗示魚其實還要更少




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