一、考查 it 用作形式主語的用法當(dāng)不定式、動名詞、從句等用作主語時，為避免頭重腳輕，通常在句首使用形式主語it，而把真正的主語放在句子末尾。如：It's no good sitting up too late. 熬夜沒有好處。
    It is quite clear that he has read the book. 很顯然，他讀過這本書。
    It doesn't matter what he says. 他說什么沒關(guān)系。
    【特別提醒】注意it用作形式主語的三類特殊句式：1.用作動詞look, seem, appear, happen, occur, follow等的主語（后接that從句或as if從句）。如：It seems that he knows everything. 他好像什么都知道。
    It （so） happened that I had no money with me. 碰巧我沒帶錢。
    2.當(dāng)系表結(jié)構(gòu)后接有if 或when引出的狀語從句時，通常在系表結(jié)構(gòu)前使用形式主語表示說話人對某情況的看法。如：It was a great surprise to me when he did a thing like that. 他這樣做使我很吃驚。
    It would be a tragedy if anything went wrong. 如果出了什么事就是一個悲劇。
    3.用于if it were not for… / if it hadn't been for…（若不是因為）。如：If it hadn't been for the freezing wind they could have reached the injured man in time. 要不是有刺骨的寒風(fēng)，他們就及時趕到傷員身邊了。
    二、考查 it 用作形式賓語的用法當(dāng)不定式、動名詞、從句等用作賓語且其后跟有賓語補足語時，就應(yīng)在賓語補足語前使用形式賓語，而將真正的賓語移至句末：We found it difficult to persuade her. 我們發(fā)現(xiàn)很難說服她。
    He makes it a rule to get up before dawn. 他習(xí)慣于天亮前起床。
    I think it very strange that he goes out walking almost every night. 我認(rèn)為他幾乎每晚都出去散步是很奇怪的。
    【特別提醒】注意it用作形式賓語的三類特殊句式：1. 動詞+it+if / when從句當(dāng)enjoy, like, dislike, love, hate, prefer, appreciate等動詞后需要接一個if或when引導(dǎo)的從句時，此時必須要先在動詞后接it作形式賓語。如：She won't like it if you arrive late. 她不喜歡你遲到。
    He hates it when people use his bike. 他討厭別人用他的自行車。
    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. 如果你能幫助我做這事，我會十分感激。
    2. 動詞+介詞+it+that從句能用于此句型的主要有三個動詞，即depend on, answer for, see to.如：You may depend on it that he will turn up in time. 你可以相信他會及時趕到的。
    I can't answer for it that the boy is honest. 我不能保證這個男孩是誠實的。
    I'll see to it that all these letters will be sent to the post before twelve. 我將注意讓所有的信件在12點以前送到郵局。