Dear Mr Zhang, I'm sorry to tell you that I'm not feeling well today. I have a fever and a headache.This morning I went to see the doctor and he told me that I had caught a bad cold. And he also asked me to stay in bed for two days. So I can't go to school today and tomorrow.

　　亲爱的张老师： 很抱歉，我今天很不舒服。我感到发烧，头痛。今天早上我去看病了，大夫说我得了重感冒。他还让我卧床休息两天。因此我今、明两天不能去学校了。