2．Some dinosaurs are thought to have lived in swamps．People think that some dinosaurs lived in swamps．

注:通过例句1和2各句的转换可以得知“to live”表示现在的情况;“to have lived”表示过去的情况。

3．When you have used the paper cups once，you throw them away．Having used the paper cups once，you throw them away．

注:在例句3中用现在分词的完成式替换了“when”引导的从句。用分词的完成式来说明“use”这一动作发生于主句的谓语动词“Throw”之前。

4．The bridge which is being built across the river is not a suspension bridge．The bridge being built across the river is not a suspension bridge．

注:在例句4中用现在分词的被动形式替换了“which”导引的定语从句,说明现在分词“being built”的动作正在进行。

5．The problem which will be discussed is what laser is. The problem to be discussed is what laser is.

注:在例句5中用不定式的一般式替换了“which”引导的定语从句,说明不定式“to be discussed ”的动作将要发生。通过上面的例子,笔者是想说明,只要在英语学习中能自觉地运用归纳,比较及辨析的方法,就能巩固所学的知识,达到灵活运用的目的。