当不定式、动名词、从句等用作宾语且其后跟有宾语补足语时，就应在宾语补足语前使用形式宾语，而将真正的宾语移至句末：

We found it difficult to persuade her. 我们发现很难说服她。

He makes it a rule to get up before dawn. 他习惯于天亮前起床。

I think it very strange that he goes out walking almost every night. 我认为他几乎每晚都出去散步是很奇怪的。

【特别提醒】注意it用作形式宾语的三类特殊句式：

1. 动词+it+if / when从句

当enjoy, like, dislike, love, hate, prefer, appreciate等动词后需要接一个if或when引导的从句时，此时必须要先在动词后接it作形式宾语。如：

She won’t like it if you arrive late. 她不喜欢你迟到。

He hates it when people use his bike. 他讨厌别人用他的自行车。

I’d prefer it if I didn’t have to do so much work. 要是我不必做那么多工作，那就太好了。

I would appreciate it very much if you would help me with it. 如果你能帮助我做这事，我会十分感激。

2. 动词+介词+it+that从句

能用于此句型的主要有三个动词，即depend on, answer for, see to。如：

You may depend on it that he will turn up in time. 你可以相信他会及时赶到的。

I can’t answer for it that the boy is honest. 我不能保证这个男孩是诚实的。

I’ll see to it that all these letters will be sent to the post before twelve. 我将注意让所有的信件在12点以前送到邮局。