者含有不定式作主语补足语的简单句。

　　据说汤姆已经回国了。

　　It is said that Tom has come back from abroad.

　　＝People say that Tom has come back from abroad.

　　＝Tom is said to have come back from abroad.

　　(9)It takes (sb.) some time to do sth.

　　该句型表示"(某人)花......时间做某事"。

　　It took me three hours to finish the work.

　　我花了三个小时才做完这项工作。

　　(10)It＋costs＋sb.＋some money＋to do sth.

　　该句型意为"某人花多少钱做某事"。

　　It cost me 80 yuan to buy the dictionary.

　　我买这本词典花了80元钱。

　　(11)It＋动词＋主语从句。

　　It never occurred to me that perhaps he was lying.

　　我从没想到过他可能是在说谎。

　　5．用作形式宾语

　　当句子的真正宾语是动词不定式、动名词或从句时，为避免句子头重脚轻，须将其放在宾语补足语之后，改用先行词it占据其原来的位置。it用作形式宾语的句型为：主语＋谓语＋it＋宾语补足语＋动词不定式/动名词/从句。该句型中宾语补足语可由形容词、名词等充当。能够用于形式宾语句型的动词有think，make，find，consider，feel，take等。

　　Marx found it important to study the situation in Russia.

　　马克思觉得研究俄国的形势很重要。

　　The ancient people took it for granted that the earth was flat.古代人想当然地认为地球是平坦的。

　　6．另外两个与it有关的常用句型

　　(1)It is/was/will be the＋序数词＋time＋that从句

　　该句型意为"这里/那是/这将是某人第几次做某事了"。

　　主句谓语动词用is时，从句用现在完成时；主句的谓语动词用was时，从句用过去完成时；主句的谓语动词用will be时，从句的谓语动词用一般现在时表示将来。

　　She understood what I was talking about，even though it was the first time we had spoken together.

　　尽管这是我们第一次在一起谈话，但是她明白我在谈些什么。

　　-Do you know our town at all?

　　--你了解我们的城镇吗？

　　-No，it is the first time I have been here.

　　--不，这是我第一次来这儿。

　　注意　句型中it可以用this或that替换，time可以用week，year，month等表示时间的名词替换。

　　This is the first month/year that I have been here.

这是我在这儿的第一个月/第一个年头。