when: Don't get excited when you talk. 講話時別激動。

　　while: We must strike while the iron is hot. 我們要趁熱打鐵。

　　as: He smiled as he passed. 他經(jīng)過時笑了笑。

　　before: It will be five years before we meet again. 要五年后咱們才能再相見。

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

　　whenever: Whenever it is possible, they play outside. 一有機會他們就到外面玩耍。

　　after: I'll tell them after you leave. 我將在你走后告訴他們。

　　until, till: I propose waiting till the police get here. 我建議等警察來了再說。