cool. Others think it will help with _______. In their life possibly________ pressure from their parents or teachers.

Some just want to see what it is like. What they don't realize is that they will get into the habit and __________ become ____________. It will then be difficult to _________ the habit. A few people ________to quit easily but for many it is a very painful process. Of course, the best way to deal with these drugs is not to start in the first place.

Keys：cigarettes；alcohol；drugs；adolescents；stress； due to；eventually；addicted ; quit；manage

Step2 Lead in

Slide show

Discovering "It"

1．It rains heavily . 指天气

2. It is 20 kilometers from Granddad's house to James'. 指距离

3. It is November 11, 2005. 指日期

4. It is 9 o'clock at night. 指时间

5. It is bad to smoke. 形式主语

6. It is no good smoking. 形式主语

7. It is likely that he will succeed. 形式主语

Step3 The use of "it"

一、"it"作人称代词

1. it的最基本用法是作代词，主要指刚提到的事物，以避免重复: