小升初必備語法：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)。

　　i have been here since 1989.

　　2) since +一段時間+ ago

　　i have been here since five months ago.

　　3) since +從句

　　great changes have taken place since you left.

　　considerable time has elapsed since we have been here.

　　4) it is +一段時間+ since從句

　　it is two years since i became a postgraduate student.