问题:
[不定项选择题]
第二篇Where Have All the Frogs Gone?In the 1980s,scientists around the world began to notice something strange:Frogs were disappearing. More recent research has shown that many kinds of amphibians(两栖动物)a
A、poisonous gases.
B、air pollution.
C、water leakage.
D、radiation.
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