The Mule（在线收听）

    A mule that had grown fat and wanton on too great an allowance of corn，was one day jumping and kicking about，and at length，cock-ing up her tail，exclaimed，“My dam was a racer，and I am quite as good as ever she was．”But being soon exhausted with her galloping and frisking，she remembered all at once that her sire was but an ass．Every truth has two sides；it is worthwhile to look at both before we commit ourselves to either．Exercises：
    回答下列问题：
    ①Why did the mule cock up her tail？
    ②Who was the mule's father？
    ③What can we learn from this fable？