逗号when引导什么从句

　　例句：

　　When will the single currency be operable?

　　什么时候实行单一货币？

　　When's food? I'm starving!

　　饭什么时候好？我快饿死了！

　　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.

　　以前我们同学时，我并不太喜欢他。

　　When is the best time to ring New York?

　　什么时间给纽约打电话最好？