阅读下面短文，在空白处填入1个适当的单词或括号内单词的正确形式。

For thousands of years people have told fables (寓言) ___41___ (teach) a lesson or to pass on wisdom. Fables were part of the oral tradition of many early cultures, and the well-known Aesop’s fables date to the ___42___ (six) century, B.C.Yet, the form of the fable still has values today, ___43___ Rachel Carson says in “A Fable for Tomorrow”

Carson uses a simple, direct style common to fable. In fact, her style and tone (口吻) are seemingly directed at children. “There was once a town in the heart of America, ___44___ all life seemed to enjoy peaceful existence with is surroundings,” her fable begins, ___45___ (borrow) some familiar words from many age-old fables. Behind the simple style, however, is a serious message ___46___ (intend) for everyone.

___47___ (difference) from traditional fables, Carson’s story ends with an accusation instead of a moral. She warns of the environmental dangers facing society, and she teaches that people must take responsibility ___48___ saving their environment.

The themes of taditional fables often deal with simple truths about everyday life. However, Cason’s theme is a more weighty ___49___ (warn) about environmental destruction. Carson proves that a simple lyric form that has been passed down through the ages can still ____50____ (employ) today to draw attention to important truths.

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