一、改变时态
例：The bell is ringing now. 一般
There goes the bell.特殊
二、改变语态
例： People suggest that the conference be put off.一般
It is suggested that the conference be put off.特殊
三、使用不定式
例： He is so kind that he can help me.一般
He is so kind as to help me. 特殊
四、使用过去分词
例： 1 She walked out of the lab and many students followed her.一般
Followed by many students, she walked out of the lab.特殊
2 Once it is seen, it can never be forgotten.一般
Once seen, it can never be forgotten. 特殊
五、使用 v- ing
1 When he arrives，please give me an e-mail.一般
On arriving /his arrival ,please give me an e-mail.特殊
2 If the weather permits ,I will come tomorrow.一般
I will come tomorrow, weather permitting. .特殊