[Rusty]

Originally Posted by Xinfu

Dear Teacher,

After looking over the presentation topics, I find that none of them is suitable for me. May I apply for a change of topic?
I would like to present on a literary work/a reading, as usual, in which case a student can talk about anything relevant as she wishes. Since the presentation accounts for only a small percentage of the final score, it would not be too much unfair to other students. But if you think it necessary, you can deduct some of the marks for giving me this special permission. Thank you. I look forward to your favourable reply.

Yours sincerely,

XF

I've edited your text to make it sound a bit more natural.