例句：

　　When will the single currency be operable?

　　什么時候實行單一貨幣？

　　When's food? I'm starving!

　　飯什么時候好？我快餓死了！

　　Some people don't know when they're well off.

　　有些人身在福中不知福。

　　I didn't use to like him much when we were at school.

　　以前我們同學時，我并不太喜歡他。

　　When is the best time to ring New York?

　　什么時間給紐約打電話最好？