六级练习2015.02.16
[audio]http://sound.yywz123.com/tingbbs/cet6/cet620150216.mp3[/audio]America’s national symbol, the bald eagle, almost went extinct twenty years ago, (1)_________________. In fact, the U.S. Fish and Wild Life Service is considering the possibility of taking it off the Endangered Species List. Once, more than fifty hundred pairs of bald eagles nested across the country, (2)_____________________________.
The chief killer was the widely used DDT. Fish, soaked up DDT, died, and were washed up on shores, (3)_____________________. DDT prevented eagle egg shells from thickening. The shells became so thin that they shattered before the babies hatched.
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