It's a long time since they left.
他们已经离开很久了。
Come on, it's time we left.
快点，我们该走了。
When I left they were all still hard at it.
我离开的.时候他们都还在努力工作。
It's not for me to say why he left.
不适宜由我说出他离开的原因。
The university is on the left bank of the river.
大学在河的左岸。