高中英语it用法归纳：强调it
 

　　19. It is + 被强调部分 + that ...
 

　　该句型是强调句型。将被强调的部分放在前面，其它部分置于that 之后。被强调部分可以是主语，宾语，表语或状语。强调的主语如果是人，that 可以由 who 换用。如果把这种句型结构划掉后，应该是一个完整无缺的句子。这也是判断强调句型与其它从句的方法。
 

　　It was about 600 years ago that the first clock with a face and an hour hand was made.
 

　　It was they that (who ) cleaned the classroom yesterday.
 

　　It was in the street that I met her father.
 

　　20. It is not until + 被强调部分 + that ...
 

　　该句型也是强调句型。主要用于强凋时间状语，译成汉语 “直到……才……”，可以说是 not ... until ... 的强调形式。
 

　　It was not until she took off her dark glasses that I realized she was a famous film star.
 

　　= Not until she took off her dark glasses did I realize she was a famous film star.
 

　　= I didn't realize she was a famous film star until she took off her dark glasses.
 

　　注意：
 

　　1)一般强调时间不能用when, 强调地点不用where;
 

　　2)强调句子谓语不能使用此句型，应使用助动词的适当形式。
 

　　3)在强调until引导的状语时，如果在句中有not，not要提前
 

　　与until连用。
 

　　1.I did meet an old friend in the street last week.
 

　　2.What I did last week was (to) meet an old friend in the street.
 

　　3.The teacher didn’t begin his class until everybody took their places.
 

　　It was not until everybody took their places that the teacler began his class.