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Step 1 Presentation

a.       Look at the link words but and however in these sentences. Then answer the questions.

1)      The report shows that we are making progress but that we need to make greater efforts.

2)      In the last ten years in China, 150 million people moved out of poverty. However, the challenges are still great.

3)      More than 1 billion people in developing countries do not drink safe water. However, in other parts of the world, e.g. Eastern Europe, water is now mostly safe to drink.

Q1. Does however mean the same as but?

Q2. Which link word begins a sentence?

Q3. Which link word can join two parts of a sentence?

Q4. Which link word is followed by a comma?

Suggested answers:

Q1. Yes.

Q2. However

Q3. But

Q4. However

b.       Look at the link words although and while in these sentences. And answer the questions.

1)      Norway is at the top of the list, while the united states is at number 7.

2)      The UK is in the thirteenth position, while China is in the middle of the list.

3)      Although more than 80% of children in developing countries go to primary school, about 115 million children are not being educated.

4)      Although developed countries give some financial help, they need to give much more.

Q1. Which sentences compare two facts?

Q2. Which sentences can you rewrite using the word but?

Suggested answers:

Q1. All of them.

Q2. All of them.

Step 2. Explanation.

a.       but and however

but 作为并列连词，在意义上起转折作用。 but 前后的两个句子或短语在意义上形成鲜明对照。 but 用来连接两个分句或两个较长的短语时， but 前面一般要加逗号。例如：

( 1 ) He is old but strong. 他年纪虽大却很强壮。

( 2 ) Learning the guitar isn't difficult, but you will have to practise.

学弹吉他并不难，但是你得练习。

( 3 ) He tried， but could not do it. 他试过，但是干不了。

however 意为“可是，然而，尽管”，较 but 的意味弱，通常用作连接性状语。其位置可以在句首，句末或插入句中。当其被用来对照两个分句时，中间需要有一个逗号;当它被用作句子的插入语时，则前后应各有一个逗号。例如：

( 4 ) However，we need not do that now. 可是，我们现在不需要做那个。

( 5 ) He said it was so;he was mistaken，however. 他说是那样的，然而他却弄错了。

( 6 ) His friends，however，had other ideas. 然而他的朋友们却另有见解。

注： however 也可用作连接副词，意为“不论怎样”，用来引导让步状语从句。例如：

However we may do it，it will be a difficult job. 无论雪下得多大，我们都必须回去。

b.       although and while

While表示两个事实之间的转折对比，although可以用but改写成另一种句子

while 用作连词时，连接两个并列句子，表示“对比”关系。例如：

He went out for a walk， while I stayed at home.

(他出去散步了，而我却呆在家里。)

I like singing while she likes dancing.

(我喜欢唱歌，而她喜欢跳舞。)

You like sports， while I prefer music.

(你喜欢体育，而我更喜欢音乐。)

although引导的从句放在主句前后均可，有时还可放在句中。

Although many difficulties are still ahead, we are determined to make greater achievements.

尽管在前面的道路上还有许多困难，但是，我们决心要取得更大的成就。

He often helps me with my English although he is quite busy.

尽管他相当忙，但是还常常帮我学英语。

although引导的从句不能与but, however连用，但可与yet, still连用。不能说：Although he was old, but he worked hard. 应把but去掉。当然，保留but而去Although也可。

c.       Conclusion

1，but与 however,

相同点：都表示转折，都可以连接两个句子

不同点: ①but还可连接两个并列的成分，however不能;

②however可置于句首，句中，句末，而且在句中时前后用分号或逗号隔开的情形较多。but往往置于句首，无需用标点符号与句子隔开。

2，although与 while

相同点：都是连词，都可引导让步状语从句;

不同点：①although意为“虽然，尽管”，相当于though，所引导的句子通常置于句首。含although从句的复合句可以转化为由but引导的并列句，但although与but不能同时出现;②while意为“然而，但是”，可用作并列连词，表示前后的对比，一般不与but转换，所引导的句子不能置于句首。

Step 3 Practice

a. 用 but， and 和 however 填空：

1. I'd like to go with you， ________， my hands are full.

2. I'm sorry， ________ I won't be able to come tonight.

3. We must finish the job in time ________ hard it is.

4. They will supply food ________ drink on Saturday.

5. It looked like rain. ________， it is clear now.

6. Building has started ______ the project will be finished by 2000.