it句型结构语法解析（二）

四、用作形式主语

1. 基本用法

当不定式、动名词、从句等用作主语时，避免头重脚轻，通常在句首使用形式主语it，而把真正的主语放在句子末尾：

Is it necessary to tell his father everything? 有必要把这一切都告诉他父亲吗?

It’s no good sitting up too late. 熬夜没有好处。

It is quite clear that he has read the book. 很显然，他读过这本书。

It doesn’t matter what he says. 他说什么没关系。

2. 几种特殊的形式主语

(1) 用作动词look, seem, appear, happen, occur, follow等的主语(后接that从句或as if从句)：

It seems as if it is going to rain. 看来要下雨了。

It seems that he knows everything. 他好像什么都知道。

It (so) happened that I had no money with me. 碰巧我没带钱。

From this witness, it follows that he must be guilty. 根据该证人的证词判断，他一定有罪。

(2) 当系表结构后接有if 或when引出的状语从句时，通常在系表结构前使用形式主语表示说话人对某情况的看法：

It was a great surprise to me when he did a thing like that. 他这样做使我很吃惊。

It would be a tragedy if anything went wrong. 如果出了什么事就是一个悲剧。

(3) 用于其他固定句型，如if it were not for…(若不是因为)，it’s time that…(该…了)等。

3. 误用形式主语的几种情形

(1) 在该用it作形式主语的地方而误用其他词：

Is ______ necessary to tell his father everything?

A. it         B. that     C. what      D. he

此题的正确答案应是A(it用作形式主语)，而不能选D。

(2) 在不该用形式主语的地方而误用形式主语：

______ must be something wrong with the machine.

A. There     B. It        C. He       D. That

此题应选A，为there be句型与情态动词must连用的情形。

比较以下两组句子：

______ is known to us all, the earth turns around the sun.

______ is known to us all that the earth turns around the sun.

A. It        B. Which                  C. As       D. That

前一句填C，as用以引导一个非限制性定语从句；后一句填A，it为形式主语，真正的主语是其后的that从句。

______ is difficult to persuade her to stay.

______ is difficult is to persuade her to stay.

A. It        B. What      C. He       D. That

前一句填A，it为形式主语；后一句填B，what用以引导主语从句。注意后一句比前一句在不定式前多了个is。

五、用作形式宾语

1. 基本用法

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。

2. 几种特殊的形式宾语

通常意义的形式宾语主要见于真正宾语为不定式、动名词、从句等且其后跟有宾语补足语时的情形，即用于“动词+it+宾语补足语+真正的宾语”这样的结构，但以下两类形式宾语却比较特殊，其后没有宾语补足语：

 (1) 由于介词后通常不能直接跟that从句作宾语，有个别特殊结构就在介词后先接it作形式宾语，再跟that从句：

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。

【注】① 在其他情况下解决介词后跟that从句的办法是借用the fact作宾语：

They were worried over the fact that you were sick. 他们为你生病发愁。

② 个别介词(主要是but和except)也可接that从句作宾语：

I know nothing about him except that he lives next door. 我只知道他住在隔壁，其他的就不知道了。

(2) 有的动词由于通常只用作及物动词，当它们后接if从句或when从句，通常应先在动词后接it作形式宾语：

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 hate it if you say such things in public. 我讨厌你在大庭广众之下说那样的事。

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。

【注】能这样用的动词不多，主要的有enjoy, like, dislike, love, hate, prefer, appreciate等表示情绪的动词。而且高考对此也有所考查，请看一道高考真题(答案选A)：

I hate ______ when people talk with their mouths full.

A. it         B. that     C. these      D. them

(3) 用于 have it that(说，认为)，take it that(认为)等个别固定表达中：

I take it (that) you agree. 我以为你同意了。

Report has it that about 30 people were killed in the accident. 据报道，在这次事故中大约有30人丧命。

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