It was good to see the young man working with his father in the fields.为什么不能用seeing?

问题描述:

It was good to see the young man working with his father in the fields.为什么不能用seeing?

to do 一般表示某次具体的动作,而doing一般表示抽象的动作.并且it作为形式主语的一般结构就是这样;it is adj to do
只有一些特殊句子才是用doing的,如:
it is no use doing sth.