例句：
When did that happen?
那件事是什么时候发生的？
They stood respectfully when he entered the room.
当他走进房间时，他们都恭恭敬敬地站着。、
We waited while he dined.
他在吃饭，我们等他。
While you are up, close the door.
你要是起来就把门关上。
I must finish off this work while the light is good.
趁这会儿光线充足我必须把这项工作完成。
