同学你好，该知识点来自沪江网校《【Uni智能】托福签95冲105分名师VIP-中级【6月签约现金奖励班】》的课程，想要更系统的学习，欢迎进入课程学习。不仅可以和更多的同学一起学习，而且还有老师、助教随时的学习指导和知识点解答哦。

同学你好~
1) 现在式：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。一般为：动词+ to do sth
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) 完成式：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)进行式：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)完成进行式：表示动作从过去到现在一直持续
She is known to have been working on the problem for many years.
大家都知道她多年来一直在努力解决这个问题。



祝同学学习进步~