【正确答案】
范文：
Dear Sir,
Please excuse my absence from class today because I got a bad cold yesterday evening and failed to sleep well at night. I felt even worse this morning. Therefore, I’had to go to the doctor to have myself thoroughly examined. Thus, I am writing to ask you for a day’s sick leave and assure you that I’11 resume my study if I feel any better tomorrow.
Sincerely,
Xiao Ming