导读：英语中有很多的固定句式，考试的时候也会考到。下文是给学生们整理的It句式，学生们平时多看，多练习，重点掌握。
第一，it作形式主语的常见句型
(1)it替代动词不定式的常见句型为：
①It+ be+ adj+ (for sb.) to do sth.
此处的形容词通常为描述事件的形容词：easy, difficult, hard, necessary, unnecessary, possible等。如：
It is illegal for a teenager to drive a car without a license.
②It +be+ adj.+of sb. to do sth.
此处的形容词通常为描述人的形容词：kind, unkind, nice, rude, cruel等。如：
It’s kind of you to help me with the problem.
(2)it替代动词-ing的常见句型：
It’s no good/use doing...
It’s (well) worth doing...
如：It’s no use crying over spilt milk.
(3)it替代从句的常见句型：
①It +be+n.+that从句如：
It is no secret that the president wants to have a second term in office.
②It +be+adj.(important, necessary, surprising...)+that从句
从句中的谓语动词用"should+动词原形"形式，且should可省略。如：
It’s important that you should apologize to her for your rudeness.
③It +v.+sb.+that从句= It +be+ v-ing +that从句如：
It worried me that she drove so fast.(= It was worrying that she drove so fast.)
④It+v.(+to sb.)+ that从句
常用动词或短语有appear, seem, come about, emerge, follow, chance, happen, occur, transpire, turn out, work out等。如：
It (so) happened/chanced that they were out.(= They happened/chanced to be out.)
⑤It +be+ v-ed +that从句
常用动词有say, report, think, believe, hope, expect, agree, accept, decide, determine, intend, plan, understand, know等。如：
It is said that the couple have gotten divorced.(=The couple are said to have gotten divorced.)
⑥It +be +v-ed + that...(should)...
常用动词有demand, request, require, order, suggest, advise, recommend等。如：
It is suggested that they should begin with the third question.
第二，it除了作形式主语外，也可以作形式宾语，如动词find, think, consider, feel, make等，这些词后常用it作形式宾语，替代其后的动词不定式或从句。此外，英语中动词appreciate, enjoy, like, dislike, love, hate, prefer等之后，常用it作形式宾语，替代其后的when/if从句。如：
I find it interesting to talk with her. 我觉得与她聊天很有趣。
I think it possible that she would like to help you. 我认为她帮助你是有可能的。
【典例1】
__is the sun that gives off light and heat, which makes __possible for plants to grow.
A. It; it B. That; those
C. This; it D. This; them
{错因分析} 如果考生对it作形式宾语及含it的强调句型掌握得不牢固，就会造成误选。
{解析} 分析句子结构可知，第一空考查强调句型的基本结构：it is/was+被强调部分+that+句子的其他部分，故用it;第二空用it作形式宾语，其真正的宾语是后面的动词不定式。答案为A项。
【典例2】
To her joy, Della earned first the trust of her students and then __of her colleagues.
A. that B. one
C. ones D. those
{错因分析} 很多考生看到横线后的of就错误地选择了B、C项，没有弄清句子要表达的意思。
{解析} 句意：使她高兴的是，Della首先赢得了她的学生的信任,然后又获得了同事的信任。空后面的"of her colleagues"与前面的"of her students"是同样的结构，因此此空应该选择that来替代the trust，以避免重复。答案为A项。
【典例3】
I’d appreciate __if you could let me know in advance whether or not you will come.(2014·陕西)
A. it B. you
C. one D. this
{错因分析} 考生如果没有掌握这个知识点"英语中动词appreciate, enjoy, like, dislike, love, hate, prefer等之后，常用it+when/if从句"，在做此题时就很容易误选选项。
{解析} 句意：如果你能够让我提前知道你是否要来，我会非常感激。根据句子的结构，此空在句中作形式宾语，而真正的宾语为if所引导的从句，故要用it。故答案为A。
第三，含it的固定用法
forget it没关系，休想，不必在意
get it 明白了，理解了，知道了
I can’t help it我没办法
make it 获得成功，幸免于难
as it is 照现状
It depends.看情况而定。
Don’t mention it.不客气。
Take it easy.别着急。
believe it or not 信不信由你
see to it that ... 确保……
depend upon it ...请相信……
take it for granted that...认为……是理所当然的
It makes no difference at all.一点关系也没有。
It’s hard to say.很难说。
It won’t do.不行。
fight it out 辩论出结果
How comes it?这是怎么搞的?
make a day of it 痛痛快快玩一整天
nothing for it 别无他法
英语不仅需要同学们平时多背诵，还需要用口语表达出来，增强语感也是学习英语的一个技巧。