it is important for him to learn to read.如何解析“to learn"和"to read"?

题目

it is important for him to learn to read.如何解析“to learn"和"to read"?

答案

It is important for him to learn to read.
这是用It 的固定句型结构之一,其中,It作形式主语,真正的主语是【for him to learn to read】,这是【不定式的复合结构】：介词+for/of sb +不定式.
原句可以转换为：
For him to learn to read is important .
而这种结构在英语中习惯上用It作形式主语.再如：
It is kind of you to help me.