when:      Don't get excited when you talk.  讲话时别激动。

　　while:      We must strike while the iron is hot.  我们要趁热打铁。

　　as:         He smiled as he passed.  他经过时笑了笑。

　　before:      It will be five years before we meet again.  要五年后咱们才能再相见。

　　after:       I'll tell them after you leave.  我将在你走后告诉他们。

　　until, till:    I propose waiting till the police get here.  我建议等警察来了再说。

　　since:       How long is it since you came to London?  你到伦敦有多久了？

　　whenever:   Whenever it is possible, they play outside. 一有机会他们就到外面玩耍。