部分That引导的主语从句，可以采用It（形式主语）+that方式进行表达，避免出现句子头重脚轻的情况。
That the price will go up is certain.
-> It is certain that the price will go up.
That the growth rate should be even less is estimated.
-> It is estimated that the growth rate should be even less.
【It形式主语】
1）It替代句子作为形式主语，引导主语从句；
2）It替代不定式短语
It takes two to tango.
It takes at least 4000 yuan to fly from Shanghai to London.
