发布时间：2017-04-17 来源：医学教育网 发布人：继续
(1) be doing sth ---- when ---
例：He was still smiling when the door opened and his wife came in.
(2) be about to do sth --- when ---
例：We were about to start when it began to rain.
(3) had not done sth --- when ---/ hardly --- when ---
例： He had not fallen asleep when the telephone rang.
(4) had just done ---- when ---
例：I had just gone to bed after a very hard day when the phone rang.