2.happen v.

　　(1)发生：

　　How did the accident happen?

　　事故是怎么发生的?

　　A strange thing happened to a friend of mine a year ago.

　　一年之前，一件奇怪的事发生在我的一位朋友身上。

　　(2)碰巧，恰好(to)：

　　I happened to meet her on my way home.

　　在回家的路上，我碰巧遇见了她。

　　I happen to know that professor.

　　我正好认识那位教授。

　　新概念英语第一册第120课课后练习答案

　　A

　　1 He dropped the vase after he had taken it into the living room.

　　2 He bought another car after he had sold his old one.

　　3 He swept the floor after he had dusted everything.

　　4 She drank the milk after she had boiled it.

　　5 He turned off the television after he had seen the programme.

　　6 He went to bed after he had done his homework.

　　B

　　1 Yes, I have just seen it. I had never seen it before.

　　2 Yes, I have just read it. I had never read it before.

　　3 Yes, I have just tried it. I had never tried it before.

　　4 Yes, I have just been there. I had never been there before.

　　5 Yes, I have just written a letter in English. I had never written a letter in English before.

　　6 Yes, I have just watched this programme. I had never watched this programme before.

　　C

　　1 It was too late. He had already painted it.

　　2 It was too late. She had already dusted it.

　　3 It was too late. You had already telephoned him.

　　4 It was too late. You had already corrected it.

　　5 It was too late. They had already shut it.

　　6 It was too late. She had already made it.

　　D

　　1 I went to the doctor after I had made an appointment.

　　2 The boss left the office after he had finished work.

　　3 My wife went out after she had finished the housework.

　　4 My teacher gave me my exercise book after he had corrected it.

　　5 My sister went on holiday after she had taken the examination.

　　6 I bought a new car after I had sold my old one.

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（编辑：何莹莹）