as, which 非限定性定语从句的用法 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Dear Ms Ma,敬爱的马老师：I apologize that I cannot go to school today. Last night my mother had a high fever and coughed badly. I think that she has got flu. She didn t have
