it is+ 形容词+of sb.+ to do sth.==sb.+ be+形容词+to do sth.
该句型中形容词用来描述不定式行为者的性格、品行等,形容词多为brave,careless,clever,polite,wrong,kind,good,nice,foolish,rude (粗鲁的),selfish(自私的)等.
It is + 形容词+ for sb.to do sth.
= It’s + 形容词 + that + sb.do sth.
在此句型中,形容词只对不定式行为者作某种描述,而不涉及其品行.这类形容词有：difficult,hard,easy,important,dangerous,possible,impossible,necessary 等.