2017-10-30 11:37 来源：小牛英语
One possible version:
I would like to know if I could ask for a leave of absence from your American Literature lesson next Thursday on account of a personal reason.
My sister's wedding will be schemed to be held then. Consequently, I am obliged to attend it. Guilt about my absence, I assure you that I will make every effort to compensate the missing lesson with the assistance of your notes and PPT. If it is convenient, I will consult you about some difficult questions.
I'd appreciate it if my request could meet with your approval.