题目内容：

假设你是李华，学校要求你们下周二下午去听一个“感动中国”人物孙家栋关于航天知识的讲座，你因故不能参加。请给你们班主任Harris发一封邮件请假。

注意：1.可适当增加细节，以使行文连贯；

2.词数100左右；

Dear Mr. Harris,

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Yours,

Li Hua