It's a long time since they left.
他們已經離開很久了。
Come on, it's time we left.
快點，我們該走了。
When I left they were all still hard at it.
我離開的.時候他們都還在努力工作。
It's not for me to say why he left.
不適宜由我說出他離開的原因。
The university is on the left bank of the river.
大學在河的左岸。