--- It’s difficult for the village children to cross the river for school.
--- 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：由题意判断是桥还没建起来。B C D 的意思是 建起来了 A 应该被建，但还没建