通常在it is + 形+for sb to do
it is + 形+of sb to do 之间进行区别
用OF表示SB is +形容词
fOR 表示to do sth is+形
it is lazy of him to have his dirty clothes washed by his sister
he is lazy to have .
it is important for us to learn English.
to learn .is important.for us引出 learn的逻辑主语