-- it's difficult tp get to the other side of the river -- l think a bridge --- over the rivera\ should be builtb\ should buildc\ will buildd\ has built请您说明理由好吗?

-- it's difficult tp get to the other side of the river -- l think a bridge --- over the rivera\ should be builtb\ should buildc\ will buildd\ has built请您说明理由好吗?
-- it's difficult tp get to the other side of the river -- l think a bridge --- over the river
a\ should be built
b\ should build
c\ will build
d\ has built
请您说明理由好吗?

-- it's difficult tp get to the other side of the river -- l think a bridge --- over the rivera\ should be builtb\ should buildc\ will buildd\ has built请您说明理由好吗?
正确答案是A,主语是bridge 与谓语动词build 是被动关系,所以这应该用被动语态.