e.g. May 4th Movement took place in 1919.

Great changes have taken place in my hometown in the last twenty years.

When will the wedding take place?

happen ：是普通用语，常指"偶然的、不可预料的"发生。用以下句型：

1) sth. happen (to sb.)：某事发生（于某人身上）

e.g. An accident happened (to him) on the road.

What do you think has happened (to her)?

2) sb. happen to do / be ...：某人碰巧......

e.g. That day I happened to be on the spot when it happened.

She happened to have no money with her.

3) It (so) happen(ed/s) that ...：碰巧......

e.g. It happened that I was out when he came to see me.

occur(occurred, occurred)：是比较正式的用语，既可指事情的"偶发"，也可指在一定的时间"发生、出现"的事情，还可表示抽象的事物，用于：sth occur to sb. / It occur to sb. that...：某人突然想到某事

e.g. When did the accident occur?

A leap year occurs every four years.

An idea suddenly occurred to him.

It occurred to me that I hadn't locked the door.

5、hard-working / hard work / work hard

hard-working：adj. 勤劳的、辛劳的

e.g. The Chinese people are a hard-working people.

Her parents are hard-working, which influences her greatly.

hard work：n. 辛苦、辛劳、艰苦的劳动

e.g. He rose to his present position through hard work.

As the saying goes, hard work leads to / results in success.

work hard：vi. 努力工作、劳动

e.g. If you work harder, you can make up for the lost time.

Work hard and you will succeed in time.

II. 重点词语和句型

1、overthrow：vt. 打倒、推翻；彻底改变

e.g. The working class are determined to overthrow the government.

They will fight on until they have overthrown the capitalist system.

n. 打倒、推翻

e.g. The overthrow of the dictator was greeted with cheers.

2、trade：vi. 做买卖、做生意、进行交易 in sth. with sb.

e.g. To trade means to buy and sell.

　　　They trade in fruit.

Our company trades with a lot foreign companies in rubber and steel.

He made his money by trading in corn.

trade (in)... for：拿......换......

e.g. He doesn't want to trade in his old car for a new one.

The natives traded diamonds and gold for daily necessities.