Dear Mr.Chris,
My name is Li Hua ,I want to apologize to you that I can't attend the American Literature Class next Monday. My mother is ill but there is no one who is available t take care of her, and she need to go to the hospital to get an body exam next Monday, so I need to go with her.
For the absence of you class, I'm very sorry. I will study it at home and finish the homework.
Yours,
Li hua