since的四種用法
1)since +過去一個時間點(如具體的年、月、日期、鐘點、1980, last month, half past six).
例如:I have been here since 1989. 1989起,我一直在這兒.
2)since +一段時間+ ago.
例如:I have been here since five months ago. 我在這兒,已經(jīng)有五個月了.
3)since +從句.
例如:Great changes have taken place since you left. 你走后,變化可真大.
4)It is +一段時間+ since從句.
例如:It is two years since I became a postgraduate student. 我考上研究生有兩年了.