I / he/ she/ it was working
we/ you/ they were working
At that time she was working in Oxford.
It was raining at 6 o'clock this morning.
What were you doing when I phoned you last night?
at 8 o'clock yesterday morning昨天早上8點，
at this time last year去年的這個時候，
...when I phoned you yesterday昨天我打電話給你的那個時候，
...while we were having the meeting我們在開會的時候。
They were watching TV when I entered the room.
The children were playing with their toys while I was eating my dinner.
He was studying in Cambridge between 1999 and 2001.
From January to March I was traveling in Egypt.
He worked from morning till night yesterday.
It was a sunny morning. Some people were sitting on the riverbank. Some were walking with their dogs. Several boys were playing football nearby...
He telephoned me, saying that his aunt was coming to see me soon.
這類動詞有 come來, go去, leave離開, start開始, stay逗留 等。主語必須是人。
We built a bridge last winter.
We were building a bridge last winter.