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?
答
to do 表示将来的，或者指一般情况，而ding sth 有特制某一次，正在进行时。
答
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.