Everyone may make mistakes in his life, no matter how old he is. But not everyone knows what to do with them, especially the young people. Here is a story for you. You may find out the answer.

    There was a little boy visiting his grandparents on their farm. He was playing with a slingshot(弹弓) in the woods one day. He practiced a lot, but he could never hit his target(目标). He felt bored and went back for dinner.

    As he was walking back, he saw Grandma's pet duck. He used his slingshot one more time. He hit the duck in the head and killed it. He was very sad and afraid. He hid the dead duck in the woods. Then he saw his sister watching him. Sally saw it all, but she said nothing. After lunch that day Grandma said, “Sally, let's wash the dishes.” But Sally said, “Grandma, Johnny told me that he wanted to help in the kitchen today, didn't you, Johnny?” and then she said to him in a low voice, “Remember, the duck!” So Johnny washed the dishes.

    After several days of doing both his housework and Sally's, Johnny couldn't stand it any longer. He told Grandma that he killed the duck. She smiled, “I know. You see, I was standing at the window and I saw what you did. But I just wanted to know how long you would be your sister's slave(奴隶).”

    My friends, have you ever made such mistakes? As the saying goes, “Who can make no mistakes?” Next time when you do something wrong, you'd better say sorry to others. Others may forgive you, too.

根据短文内容，判断正误