sb.had hardly(=scarcely) done sth.when...=Hardly / Scarcely had sb.done sth.when. 只能用when 的句型: 放句中,主句是进展时,从句是短暂动作,表示这时突然 从句是短暂动作:When I got up, I heard the bell ring. 当我起床的时候,我听见铃响了。 只能用while的句型: 1. 表示对立予盾的比照,这时while相当于but。I am poor while you are ,你却很富有。 2. 表示“趁着还来得及的时候,赶快.... while it is hot. 只能用as的句型: 属以下情形时,只用as, 而不用when或while。 A) 用于表示同一个人的两种动作交替进展,指“一边……,一边……“。如: He looked behind from time to time as he went forward. B)表示两个同步进展的动作或行为,译为“随着……“。如: As children get older, they become more and more interested in the things around them.