(1) The boy was walking down the street when the UFO landed?
(2) While the boy was walking down the street, the UFO landed.
(3) The girl was shopping when the alien got out.
(4) While the girl was shopping, the alien got out.
1. 构成：过去进行时由 “was / were +动词-ing”构成
— What was he doing when the UFO arrived? 当UFO落地时他正在干什么？
— He was sleeping late when it arrived. 当UFO落地时她正在熟睡。
Many people remember what they were doing on April 4, 1968.
(1) at 9 o'clock yesterday, from 8 to 9 yesterday morning, at this / that time yesterday, this morning, the whole morning, all day yesterday, when, while, 如：
We were having an English class at 9 o'clock yesterday.
Xiao Ming was sleeping all day yesterday.
(2) 主句（过去进行时）＋ when + 从句（一般过去时）
(3) 主句（一般过去时）+ while +从句（过去进行时）
The girl was shopping when her friend saw her.
The dog got out of the box and ran away while Linda was buying the newspaper at the station.
肯定式：I / He / She / It was working.
We / You / They were working.
否定式：I / He / She / It was not working.
We / You / They were not working.
— Was I working? — Yes, you were. / No, you were not.
— Were you working? — Yes, I was. / No, I was not.
— Was he / she / it working? — Yes, he / she / it was. / No, he / she / it was not.
— Were you / they working? — Yes, you / we / they were. / No, you / we / they were not.
注：was not常缩略为wasn't; were not常缩略为weren't.
David wrote a letter to his friend last night.
David was writing a letter to his friend at 8 last night.
■表示过去将来，多用于go, come, leave, start, take off等动词。如：
He said he was leaving for home in a day or two.
She was always thinking of others. 她老是想到别人。（赞扬）
She was forever complaining. 她老是抱怨。（厌烦）
When the UFO took off, the boy was taking photos.
Mary was having dinner when I saw her.
The boy was still sleeping when his mother got home yesterday morning.
While the boy was taking photos, the UFO took off.
The weather was fine while we were in Beijing.
While we were swimming someone stole our clothes.
Don't talk so loud while others are working.
I was doing my homework while he was listening to music.
注：通常不能用于过去进行时的动词主要有：agree, is, am, are, believe, belong, care, forget, hate, have (拥有), hear, know, like, love, mean, mind, notice, own, remember, seem, suppose, understand, want, wish等。
对于初二学生来说，熟练掌握过去进行时的构成、意义、标志词和过去进行时的各种句式是很容易在英语考试中取得高分的，但是要掌握好一般过去时与过去进行时的区别，when 与while的不同之处，也是需要下一番功夫的，这需要在大量的习题中掌握其技巧，但只要牢记when 与while的这两种从句，即：主句（过去进行时）＋ when + 从句（一般过去时），主句（一般过去时）+ while +从句（过去进行时）对于做题也是很有用的。
(1) We were listening to the teacher when she came in. (对划线部分提问)
_____ _____ you _____ when she came in?
(2) He does his homework every day. (用at this time yesterday改写句子)
He ____ _____ his homework at this time yesterday.
(1) _____ Tom was eating supper, it began to rain outside.
(2) Don't use your cell phone _____ you are driving a car.
(3) What were you doing _____ Mr. Zhou came in?
(4) Jim is good at math _____ Mary is good at English.
(5) We were watching TV_____ the electricity was off.
(1) I first met Lisa three years ago. She ___ at a radio shop at the time.
A. has worked B. was working
C. had been working D. had worked
(2) My mother was reading while I ___ the music.
A. listened to B. listened C. was listening to D. is listening to
(3) I ___ my breakfast when the morning post came.
A. had B. had been having
C. have been having D. was having
(4) When I arrived at his office, he ___ on the phone.
A. was speaking B. spoke
C. had been speaking D. had spoken
(1) Lucy 和Lily昨天下午从3点到4点在游泳。
Lucy and Lily ______ ________ from 3:00 to 4:00 yesterday afternoon.
(2) 当Mr Cook到家时，他正在听收音机。
When Mr Cook got home, his son ______ ______ to the radio
While Li Lei ______ ______________, Jim came in.
(1)The boy with his parents _____when the earthquake rocked their city.
A. were sleeping B. is asleep C. was sleeping D. are asleep
本题易错点之一在于介词“with”的用法掌握较差。A with B的谓语动词应与A 一致，为单数形式；易错点之二在于没有遵循“when”引导的时间状语从句的主句用过去进行时从句用一般过去时。因此正确答案为C。
(2) The policewoman asked the man ___ at 9:00 o'clock last night.
A. what is he doing B. what he is doing
C. what was he doing D. what he was doing
(3) When you_______ (konck) at the door yesterday, I_________ (do) some washing.
本题关键要弄清“when”与“while”后所跟的动词。“when”既可接时间点也可接时间段，“when”引导的时间状语从句中的动词可以是终止性动词，也可以是延续性动词，所以主句用过去进行时，从句应用一般过去时；“when”从句中的动作既可以与主句的动作同时发生，又可在主句的动作之前或之后发生。而“while”接一段时间，从句中的动作必须是延续性动词，从句中的动作与主句中的动作同时发生，主从句都用过去进行时的多。所以正确答案为：knocked; was doing.
(1)What were; doing (2)was doing
(1) while (2) while (3) when (4) while (5) when
(1) B (2) C (3) D (4) A
(1) were swimming (2) was listening (3) was having breakfast