Isn't it very kind your parents to do that for us?A. for B to C. about D. of

问题补充：

Isn it very kind your parents to do that for us?

A. for B to C. about D. of

答案：

解析：本题是固定用法的考查。It is+形容词+of/for+sb．+t0 do是固定的句型。但两个句型用法不同，如果形容词表示人的性质，如kind，nice等必须用of。