when
单词辨析：
所引导的状语从句中，谓语可以是延续性动词，也可以是瞬时动词，其动作既可以和主句的动作同时发生，也可以在主句的动作之前或之后发生。
He got engaged to Lucy when travelling last autumn.
去年秋天旅行时，他与露西订了婚。
It was raining when we arrived.
我们到的时候正在下雨。
Turn off the switch when anything goes wrong with the device.
如果装置出故障，就把开关关掉。
引导状语从句时，侧重指从句中的动作与主句中的动作同时发生或同时进行，一般持续时间不长，其谓语可以是延续性动词，也可以是瞬时动词。
She was coming in as he was going out.
她进来的时候，他正要出去。
I caught a whiff of perfume as she swept past me.
她从我身边走过时，我闻到一股香水味。
Joe jumped onto the bus just as it was pulling away.
正当公共汽车开动时，乔跳上了车。
指在某事发生之际或发生的过程中，另一事又发生。所引导的状语从句中，谓语应为延续性动词，而不用瞬时动词，强调其动作与主句中的动作同时发生，但持续时间一般较长；有时也可指主句的动作在从句的动作过程中发生。
Don't interrupt him while he is thinking.
他在思考时别去打搅他。
She got married while working as a waitress.
她在饭店当服务生期间结婚了。
Pat killed time by watching TV while waiting for her.
帕特在等她时边看电视边打发时间。
相关例句：
He could remember a time when he had worked like that himself
他还能记得自己一度工作起来也是那个样子。
The driver lost control when a tyre burst
一个车胎爆了，司机失去了控制。
'I'll be there this afternoon.' — 'When?'
“我今天下午会去那里。”——“什么时间？”
I asked him when he'd be back to pick me up
我问他什么时候回来接我。
I don't know when the decision was made
我不知道决定是什么时候作出的。
When were you in this house last?
你最后一次在这房子里是什么时候？