進行時態或一般將來時態
1、was/were doing +when 意思為“就在這時，正在這時”。
如：
I was walking in the street when someone called me from behind. 我正在街上走，就在這時有人從後面叫我。
They were discussing the problem when the teacher came in. 他們正在討論問題，就在這時老師進來了。
& about to 意思為 “正要/正準備做某事，就在這時……”。
如：
She was about to go out when an unexpected visitor came. 她正準備出去，這時來了一位不速之客。
We were about to set out when it began to rain. 我們正要動身，就在這時開始下雨了。
&+表示狀態的介詞短語+when意思為 “正在做某事，就在這時……”。
如：
They were at work in the office that afternoon when a big fire broke out.那天下午他們正在辦公室工作，就在這時一場大火發生了。
We were on duty in the classroom when a boy rushed in. 我們正在教室裏值日，就在這時一名男孩衝了進來。
Li Ping was on his way home when two boys stopped him.李平正往家走，突然兩個男孩攔住了他。
1、將when翻譯成當……時候，此時主句與從句時台一樣.2.將when翻譯成……就在這時.有三個常用句型 doing ……正在做什麼，就在這時
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