如何区分it is 是强调句还是形式主语

1、强调句的用法1.强调句it is not +连词It was not until hi衡痕贤伎s wife came back that he went to bed.直到他的妻子返回，他才去睡觉。2.强调句it was+时间状语It was last night that his mother worked at factory正是昨晚，他的母亲在工厂里工作。3.强调句it is +宾语（或者人）It is Li Lei’s brother that you met in the street yesterday.你昨天在街上所见到的就是李雷的兄弟4.it is+接地点状语it is street that you met lilei's brother yesterday你昨天在街上遇见的是李磊的兄弟5.it is +名词（人）it is this man who gave me the food给我食物的是这个男人.6.it is+宾语(人)it is this man whom I met in the street我在街上遇到的是这个男人.强调句通常是it is 接名词(人).状语.宾语.连词表示强调句

2、形式主语的句子1.it is+形容词it is diffcult to do the work。做这个工作是非常困难的。it做形式主语。2.it is+形容词+thatit is surprise that you give me the gift你给我这个礼物是非常惊讶的。3.it is+名词it is an honor that president give me the gift总统给我这个礼物是一个荣幸.4.it +不及物动词 +thatit seems that this thing is true似乎这个事情是真的.5.it is接过去分词it is said that the pirates buried the treasure in the ground据说，海盗绑宝藏在这个洞里.形式主语通常接接名词 形容词 不及物动词 过去分词