GWD

felifeli · 发表于 2010-3-30 12:49:35

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.

看不明白,谁给解释一下,总觉得D会是fish数量增加啊,怎么能解释减少呢?

sofarlee · 发表于 2010-3-31 01:08:04

D它说干旱时，alligators挖洞使水充足，这样子就可以使鱼蛋正常孵化。现在alligators的数量下降了，自然没有去挖洞存水了，这样鱼蛋也就无法孵化，从而鱼的数量也下降了。

felifeli · 发表于 2010-3-31 13:33:27

晕倒~~ 原来是没挖洞的了呀
我怎么就没想到这层呢
多谢解答哈!

GWD

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