SINCE的用法具体的
问题描述：
SINCE的用法具体的
答
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）.例如：
I have been here since 1989.1989起,我一直在这儿.
2） since +一段时间+ ago.例如：
I have been here since five months ago.我在这儿,已经有五个月了.
3） since +从句.例如：
Great changes have taken place since you left.你走后,变化可大了.
Great changes have taken place since we were here.我们走后,变化可大了.
4） It is +一段时间+ since从句.例如：
It is two years since I became a postgraduate student.我考上研究生有两年了.