when在表示突然是的用法?

Question

when在表示突然是的用法?

Answer 1

when表示前面的叙述所没有提到过的信息.它总是对所描述的事件予以引人注目的强调,意为“这时；突然”；当位于句末的分句具有引种用法时,大致有以下三种情况：
A.when 分句前面的分句使用过去进行时.
如：（ 1 ） He was still smiling when the door opened and his wife came in.他正笑着的时候,门突然开了,他妻子走了进来.
（ 2 ） I was thinking of this when I heard my name called.我正想着这件事时,突然听到有人叫我的名字.
B.when 分句前面的分句使用 was （were） about to,was （were） on the point 等.
如：（ 1 ） We were about to start when it began to rain.我们刚要出发就开始下雨了.
（ 2 ） He was on the point of leaving when someone knocked at the door.他刚要走就有人敲门.
C.when 分句之前的分句用过去完成时,其中 sb had hardly / scarcely /barely … when 已成为固定词组.如：
（ 1 ） We had hardly fallen asleep when the bell rang.我们刚刚入睡,铃声就响了起来.
（ 2 ） He had scarcely arrived when he had to leave again.他刚刚到达就又要离开了.