增加：在缺漏词的地方加一个漏字符号，并在其下写出该词。

删除：把多余的词用斜线划掉。

修改：在错的词下划一横线，并在该词下面写出修改后的词。

注意：1). 每处错误及其修改均仅限一词。

2). 只允许修改10处，多者（从第11处起）不记分。

Dear Mandy,

    I'm not doing well in my lessons at school, especial in maths. My dad says I must try hard because he wants me go to university. He thinks I'm lazy, but it's not true. I work really hard, often study late into the night! I've tried to talk to my mother, but she always said I have to work as hard like my brother does. My brother doesn't study very hard, and he always gets excellent grades. It's not fair! The only thing I like it is art. My teacher says I'm the best student she's had for year. When I told my dad，all he said was, “You mustn't waste your time in art. You must focus your mind on your lessons!” I'm feeling quite puzzling as to what to do now. Would you please help me out?

    Thanks a lot!

Yours,

Lisa

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已知一组数据0，﹣1，1，2，3，则这组数据的方差为（　　）