阅读理解C
    Mr. Smith works in a big city. Mrs. Smith teaches English in a small town(镇). Bill is their son．He is with his mother．
    It's a sunny Monday morning. Mrs. Smith writes a letter(信) to Mr. Smith．She says，"Bill， take the letter to the post office (邮局)and your father will get it on Friday．"
    After a very long time，Bill comes back home．
    "Why do you come back so late? Did you play basketball with your friends?" asks Mrs. Smith．
    "No, Morn," answers Bill, "I went to the post office in South Street．"
    "Why did you go there? There is one near our house．"
    "Butthe onein South Street is near Dad．He can get the letter earlier(更早地)．"
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