【—since的】since的后面一般可以加一段时间、一个时间点或者是一个从句的四种用法。

　　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.

　　关于since的四种用法是我们在英语中几乎是随处可见的，所以同学们不可以马虎了。

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