—What should we do first if we want to develop our village? —A lot of new roads I think.

问题补充：

—What should we do first if we want to develop our village?

—A lot of new roads, I think.

A. have to build B. must build C. must be built

答案：

解析：本题考查的是被动语态，情态动词的被动语态结构为主语+情态动词+be +动词的过去分词，故选C