单选题 --They haven't finished the work up to now.
--Well, they ______.
A. should B. should have
C. would D. must have

【正确答案】 B
【答案解析】[解析] should have done意为“本应该做某事(但实际上没做)”。故选B。句子意思是：一他们到现在还没有完成工作。—唉，他们本应该完成，却没完成。