The teacher asked me what I don’t understand about this problem.

2.介词宾语

Whether he can deal with the matter lies in the way that he communicate with others.

3.作形容词宾语

I’m convinced that that you can recover this painful experience.

4.it作形式宾语:动词+it+that

He makes it possible to overcome these enormous difficulties.

to do不定式to省略的情况

1.主语部分有动词do出现时,用作表语的不

定式可以省略to.

The first thing he can do is to close all the window in the classroom.

她首先关上教室内的所有窗户。

2.并列不定式与to的省略

当两个或多个作用相同的不定式并列时,通常只需在第一个不定式前用 to,其余不定式前的to可以省略.

It is strange that he should try his best to help her and support her.

奇怪的是，他竟然使尽全力帮助和支持她。