苏州韦博讲解since的四种用法

苏州韦博讲解since的四种用法

　　1)since+过去一个时间点(如具体的年、月、日期、钟点、1980,last month,half past six)。
　　I have been here since 1989.
　　2)since+一段时间+ago
　　I have been here since five months ago.
　　3)since+从句
　　Great changes have taken place since you left.
　　Considerable time has elapsed since we have been here.
　　4)It is+一段时间+since从句
　　It is two years since I became a postgraduate student.