Dear Mr.(男)/Mrs.(已婚女)/Ms.(未婚女) xxx(批你假的人的姓),I am writting to request absence during the Lesson of Chemistry in afternoon 5th of May. There is to be a Sports Part of a Senior High School Entrance Exam in my former school by then, I suppose it would be quite helpful if I could attend and contribute my little cheer up to them. I will return immdiately and continue the next lesson once the exam is finished, of course, if my request is granted.I appreciate your attention and considerationRegards, xxxn你的名字英语文化中,应用文说话开门见山,所以先说你要请假,再解释原因,I will return immdiately and continue the next lesson once the exam is finished, of course, if my request is granted. 如果我的请假被批准,我会在考试结束后第一时间赶回来继续后面的课程(这句话你可以自己决定是否使用)英文国家中体育一般用sport表示,而不是p.e, I appreciate your attention and consideration, 不论请假是否被批准,感谢他花时间看你的请假条。Regards, xxxn你的名字 (你写的内容不是很复杂,冗长,严肃,他也不是和你很亲密的人,所以不用sincerely yours 或者 faithfully yours 或者 yours, yours在英语文化中表示忠诚的意思,一般这种简单的事情,普通的关系不用,否则看你信的人会有压力)祝你请假成功