How do i persuade my teacher to change my grade?

Ok i have an 89.8 in reading and I work hard .I had one bad day and go t a D on a tes.t I tried to get her to change it so she said write a persuasive essay to persuade her into changing it.Can you help me?How do i persuade my teacher to change my grade?
Well,one good reason is what you already said,that you have always worked hard in her class,also you could tell her all the bad things that happened to u that day(for ex,you could tell her that you had many homeworks 2 do and that night u went very late 2 bed or something like that) and u could also say that u are good in reading and u dont deserve such bad grade.I hope help u with that,that's just what I have on maind right now.How do i persuade my teacher to change my grade?
You could redo the test for the essay (assuming it was an essay test to being with and not, say, a multiple choice or fill in the blank test where all you have to do is look up the answer) to convince her that you know the material.
I would do the essay. In the essay explain to her that you had a bad day and tell her how important it is to you that you have at least a 90 average. Explain to her that you know that it is very important to you and your future. I am sure it is frustrating but it is worth it in the long run. Good luck