difficult to cure，if we use the cloning technology，we can change the order of genetic DNA，so we can save lots of people.

But cloning still has some problems. The scientists found that the cloning animal's gene is a little different from the original animal's. So its life will be shorter than the real life. The fact has proved that-the cloning sheep Dolly died. It only has the half life of the common sheep. 　　　　　　　　　　　　　　　　　　　　　　

[知 识 梳 理]

Ⅰ. 核心单词

一、单词拼写

1．They think the cloned animals like Dolly the sheep，which ________(总共) lived only six years and a half，can't live a normal life.

2．Old people are usually more________(保守的)than young people.

3．The scientists are struggling for a ________(突破)in cancer research.

4．We have worked out a new set of________(程序)for using this machine.

5．The area has remained untouched by________(商业的)development.

答案　1. altogether　2. conservative　3. breakthrough　4. procedures

5．commercial

二、单句语法填空

1．You mentioned that you could teach English as a reward，which is ________(exact)what I want.

2．I just need to make a few ________(correct)and then we can send it to the printer.

3．You can complain，but I doubt whether it will make any ________(differ)．

4．Would you like to do me a favour ________(send)an e­mail to my grandson?

5．My father supported me in taking part in more social activities，________my mother objected to it.

答案　1. exactly　2. corrections　3. difference　4. to send　5. while

Ⅱ. 重点短语

一、补全短语

1．________ the time一直，始终

2．pay ________得到好结果；取得成功；偿清