It is polite ______ to other people's question.A.answer.B.to answer.C.reply.D.to reply为什么不能选B？
问题描述：
It is polite ______ to other people's question.
A.answer.B.to answer.C.reply.D.to reply
为什么不能选B？
答
D to reply
形式主语 It is +形容词+to+动词原形
answer是及物动词可以直接 answer question