—People find it hard to get across the river—I think at least two bridgesover it．A. needB

问题补充：

—People find it hard to get across the river．

—I think at least two bridgesover it．

A. need

B. are needing

C. will need

D. should be needed

答案：

A. need

B. are needing

C. will need

(答案→)D. should be needed

解析：本题的含义是在河上至少需要两座桥，本题桥在从句作主语，是动作的承受者，故被动结构，结构为be+过去分词，need的过去分词是needed，故选D。