was eating,ran
was repairng,called
was having,knocked
was sweeping,came
had begun.
when引导状语从句,表示多种语法意义：
1.表示时间,意为“当……时；在……的时候”.
A.在时间、条件等状语从句里,用一般现在时表示将来时；当需要表达将来完成的意义时,必须使用现在完成时来代替.
如：（ 1 ） When you see him,please say hello to him.见到他时,代我问他好.
（ 2 ） When you have finished your experiment,please tidy the lab and put everything back in the cupboards.当你们做完实验后,请把实验室整理好并把物品放回柜子中.
B.表示过去发生的事情,在 when 引导的时间状语从句的主从复合句中,动作发生在先的用过去完成时,在后的用过去时.
如：（ 1 ） When I was in Japan,I bought some beautiful pearls.我在日本时,买了一些漂亮的珍珠.
（ 2 ） When I reached the station,the train had left.当我到达火车站时,火车已经开走了.
2.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.
3.表示条件,相当于 if ,引导条件状语从句.
如：How can I get a job when I can't even read or write?如果我连读和写都不会,我怎么能找到工作呢?
4.表示对比,主要有以下两种情况：
A.相当于 whereas,while,since,意为“既然；然而”.
如：（ 1 ） How can I help them to understand when they won't listen to me?既然他们不愿听我的,我又怎么能帮助他们弄明白呢?
（ 2 ） They have only three copies when we need five.他们只有三本,而我们却需要五本.
B.when 从句中使用虚拟语气,意为“本来……却……”.
如：（ 1 ） She paid when she could have entered free.本来可以免费入场,而她却付了款.
（ 2 ） She stopped trying when she might have succeeded next time.她本来下次有可能获得成功,但她却不再尝试了.
（ 3 ） They were gossiping,when they should have been working.他们本该工作,却在那里说别人的闲话.
5.由 when 等引导的状语从句,如果主语与主句的主语一致或是 it ,谓语动词又含 be 动词时,主语和 be 动词常常被省略,就变成“ when + V-ing/ V-ed/ adj/ 介词词组”的结构.
如：（ 1 ） When in Rome,do as Romans do.入乡随俗.
（ 2 ） When （we are ） young,we are full of hope.年轻时,我们大家总是充满希望.
（ 3 ） Don't reach sideways when standing on a ladder.站在梯子上时,不要侧着身子去够东西