参考：无忧英语51talk梁颖老师的超实用语法20讲在线课程第4课
lesson 4时态 ：过去进行时
形式：was/were+现在分词
现在分词变化规则：
1)一般情况+ing，going, playing,
2)不发音的e，去e+ing，taking, writing, leaving, breaking, making,
发音的e，seeing
3)ie结尾，变ie为y+ing, lie--lying, die--dying, tie--tying
4)重读闭音节“辅元辅”，双写末尾+ing, cutting, beginning, forgetting,
常见用法：
1)过去某时正在发生的事情
--did you see a man in black pass by just now?
--No, I was reading a newspaper.
I was watching TV at 8:00 last night.
2)在过去一段时间内持续发生的动作
Father:I promised to buy you a car if you passed your exam, but you have failed. what were you doing last term?
Son: I was learning to drive a car.
I was learning to play the piano at that time.
3)设置故事背景
In a Gothic castle, it was getting darker. the rain was beating on the windows. the wind was rising. A wood fire was burning on the hearth, and a cat was sleeping in front of it. A girl was playing the piano and was singing softly to herself. Suddenly, there was a knock on the door.
Once upon a time, a very old lay was living in the palace.
经典句型：--was doing---when---did---正在--突然---
I was having a nice dream when the alarm clock rang.
I was watching TV when my mom came home.
I was walking on the road when I saw a beautiful girl ahead.
I was walking towards her when I found he is a man.
Were they listening to the broadcast when you entered the room?
4)委婉的请求
--I was wondering if you'd like to lend me your car.
--I'll buy you one! wait!!
I was wondering whether you would go to the party with me?
练习(一般过去时和过去进行时）：
I saw Ted at the student cafeteria at lunchtime yesterday. He was eating a sandwich and talking with some friends. I joined them.
Late yesterday afternoon while I was preparing the dinner, the doorbell rang. I put everything down and rushed to answer it. I opened the door and found a delivery man standing in my doorway.
he was holding an express mail package and needed me to sign for it. While I was dealing with the delivery man, the phone rang. I excused myself and reached for the phone.
While I was trying to talk on the phone and sign for the package at the same time, my young son ran up to me to tell me about the cat. the cat was trying to catch a big fish in my husband's prized aquarium. the fish was swimming frantically to avoid the cat's paw.
I wasn't sure if he was really interested or if he was being polite.
--Have you finished reading Jane Eyre?
--No, I was doing my homework all day yesterday.