---It’s difficult for the villagers to cross the river.
---I think a bridge over the river.
A. should be built
B. is being built
C. has been built
D. was built
网友回答
(答案→)A. should be built
B. is being built
C. has been built
D. was built
解析：本题考查的是情态动词的被动语态，其结构为主语+情态动词+be+动词过去分词，故选答案为A