March 6th, 20xx
Dear Mr Li,
李老师：
I’m sorry to tell you that I have to ask for sick leave for the whole afternoon class. Because I have a heavy headache now and feel very sick. I think I have to ask for sick leave to go to hospital for medicine. I will attend the next day classes on time.
我很抱歉地告诉你，我想请一整个下午的病假。因为我现在头很疼而且感觉很难受。我觉得我必须得请假去医院看医生。我会准时参加明天的课。
Yours repectful,
Tim
蒂姆