現在完成時態中since的用法

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)。

I have been here since 1989.自從1989年起，我就已經在這了。

2) since +一段時間+ ago

I have been here since five months ago.自從五個月以前，我就已經在這了。

3) since +從句

Great changes have taken place since you left.自從你離開後，這邊發生了很大的改變。

4) It is +一段時間+ since從句

It is two years since I became a

postgraduate student.

以上是所有回答，希望幫到您。