the problem is difficult ___ .
问题描述：
the problem is difficult ___ .
a.to solve
b.to be solved
c.being solved
d.to solving
写出原因!
答
A主语（人,物） + be + 形容词+ to do (不定式主动式）此句型中的主语是后面不定式的逻辑宾语,所以不定式不用被动式再如：The question is easy to answer.这问题很容易回答He is hard to deal with 他难相处The app...