before是過去式標誌嗎

before不是過去式標誌

例句

1、

So it's happened before， and it will happen in the future

這樣的事情在以前發生過，在將來還會發生

2、

It's happened before， there were two government shutdown in the mid 1990s.

這在以前就曾經發生過，在1990年代中期有兩個政府關閉。

3、

Interconnectivity allows for the possibility of a reading experience that was barely imaginable before.

互聯性使我們有可能擁有在以前幾乎是無法想象的閲讀體驗。