一般式　　　　　 to do　　　　　　to be done

　　进行式　　　　　 to be doing

　　完成式　　　　　 to have done　　 to have been done

　　完成进行式　　　 to have been doing

　　1) 现在时：一般现在时表示的动词，有时与谓语动词表示的动作同时发生，有时发生在谓语动词的动作之后。

　　He seems to know this.

　　I hope to see you again. = I hope that I'll see you again.　我希望再见到你。

　　2) 完成时：表示的动作发生在谓语动词表示的动作之前。

　　I'm sorry to have given you so much trouble.

　　He seems to have caught a cold.

　　3) 进行时： 表示动作正在进行，与谓语动词表示的动作同时发生。

　　He seems to be eating something.

　　4) 完成进行时：

　　She is known to have been wreaking on the problem for many years.