Question

It's+形容词+for sb +to do sth与It's+形容词+of sb to do sth的区别

Answer 1

“It is +adj+for sb to do sth.”句型和“It is +adj+of sb to do sth.”句型

这两个句型中的it为形式主语，代替后面的动词不定式。我们一般用for 或of导出后面动词不定式的逻辑主语，for和of的选择关键取决于前面的形容词，
如果该形容词指人的品质特征，一般用of，如kind,nice,friendly,clever,foolish,polite等词；
如果该形容词说明行为动作的品质特征，则用for，如important,difficult,easy,necessary，impossible,hard等词。请比较。

It’s very kind of you to help me with my English.你真好，帮我学英语，。

It’s clever of you to work out the maths problem. 你真聪明，解出了这道数学题。

It’s very dangerous for children to cross the busy street.
对孩子们来说，穿过繁忙的街道很危险。
It’s difficult for us to finish the work. 对我们来说，完成这项工作很困难。

【注意】

“It is +adj+of sb to do sth.”句型通常都可转换为不定式作状语的句子，但“It is +adj+for sb to do sth.”句型不可以。例：
It’s very nice of you to offer me a seat.
= You are nice to offer me a seat. 十分感谢你给我让座。
It is careless of him to lose so many things.
= He is careless to lose so many things. 他丢了这么多东西，真是太粗心了。

Answer 2

你看看句子能不能变为sb. is adj. to sth.
如果能，用of， 不能，用for
比如：可以说You are wise to do sth.
因此用It's wise of you to do sth
但是不能说You are necessary to do sth
因此用It's necessary for you to do sth