形式主语it的5种用法是什么
本文中，我为大家整理了形式主语it的5种用法，快来看看吧！
it的5种用法
1、指代性it一般是指人称代词it，it作人称代词时可指代事物、动物、婴儿、未知的人或一件事。
2、不定式作主语，It's my pleasure (to help you).
3、it做先行词。
4、it做形式宾语。
5、引导强调句的it。
it做形式主语基本句型
1.It+be+形容词+主语从句，如：It is uncertain whether he can come to Jenny’s birthday party or not.
2.It+be+名词词组+主语从句，这类名词有：a fact,a pity,a shame,an honour，a question等，如：It’s a pity that you missed the exciting football match. It remains a question whether he will come or not.
3.It+be+过去分词+主语从句，这类过去分词有：announced,believed,expected,hoped,decided,reported,said, shown等，如：It is reported that 16 people were killed in the earthquake. It is not decided who will give the operation to the patient.
4.It+不及物动词(seem,appear,happen等)+主语从句,这类不及物动词有：appear,happen,seem等，如：It seemed that he didn’t tell the truth. It happened that I was out when he called.
5.It+be+形容词+for sb.）+动词不定式这类句型常用形容词easy,difficult,hard,important,possible，wise等作表语，有时候为了强调不定式动作的执行者，常在不定式前加for sb，如：It’s necessary for the young to master two foreign language. It is unwise to give the children whatever they want. 这类形容词有：easy, difficult, hard, important, possible，wise
