问题补充:
--- 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
答案:
(答案→)A. should be built
B. is being built
C. has been built
D. was built
解析:句意:--对于山村的这些孩子穿过这条河上学是困难的,---我认为一座桥应当在在河的上面,should be done应当被允许做某事根据题意故选A。