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    Billy has a dream. He wants to fly(飞) like a bird(鸟). His mother tells him, "You can't fly like a bird because you are too big." "Why can't I? Some birds are big, but they can fly!" The boy doesn't understand（理解）.

    Cathy is crippled（跛的）. She wants to walk and run like other kids. " Why can't I walk or run like other children?" Cathy thinks.

    One day, the two children meet in a park. " Do you want to fly like a bird?" Billy asks Cathy. "No," Cathy says, " I only want to walk and run like you."

    Then Billy walks to Cathy's father. He asks, "___________ ?". " That's OK," says the father.

    Billy goes to Cathy and says, " Get on to my back（爬到我背上）. Let's run.," Then Billy runs with Cathy on his back. Cathy is very happy and says, " We can fly, Billy! We can fly!"