Isn’t ______ rude _______ him to talk to his mother like that?
A.that; forB.he; ofC.it; forD.it; of在线课程D
本句中it为形式主语（值得注意的是只有it才能充当形式主语），真正的主语为不定式短语，不定式的逻辑主语常用介词for或of引出。形容词rude和him之间有内在联系，故用介词of。