1. *when 引导突然发生的动作，意为：正在那时…
We were eating when a friend came to see me. (我们正在吃饭，正在那时一个朋友来了)
2. *hardly/ scarcely/ barely …when 句式 ， 意为：一…….就….
no sooner …than
I had hardly fallen asleep when the telephone rang. 非倒装句 (我刚一睡着,电话铃就像了)
I had no sooner fallen asleep than the telephone rang.
Hardly had I fallen asleep when the telephone rang. 倒装句
No sooner had I fallen asleep than the telephone rang.
