【正确答案】Dear Prof. Lewis,
I caught a bad cold last night. I am having a fever and still lying in bed. I took the temperature and it read 40℃. A doctor was sent for this morning. He gave me some medicine and advised a rest of three days.
I am writing to you to ask for sick leave. I cannot attend your linguistics lecture on Wednesday and Friday. I will ask my classmate Zhang Hong to lend her notebook to me in order that I make up the missed lesson.
Enclosed is the Doctor's Certificate of Advice.
　　　　　　　　　　　　　　　　　　　　 Sincerely yours,
　　　　　　　　　　　　　　　　　　　　 Li Ming