敬爱的马老师：
I am sorry to tell you that I can't go to school today. Last night my mother had a high fever and a bad cough. Perhaps she has caught flu. I will take my mother to Tiantan Hospital and then look after her at home, so I couldn't go to school today. So I would like to ask for one day's leave. I will be very grateful if you grant my leave.
很抱歉我今天不能去上学了。昨天夜里我妈妈发高烧，咳嗽得厉害，她可能得了流感。因为今天我要带妈妈去天坛医院，然后在家照顾她，所以不能去上学了。因此我想跟您请一天假。如果您能准假我会非常感激。
Yours,
Li Li
您的学生
李丽