问题补充：
We such great success without your efforts. Thanks a lot.
A. shouldn’t have accomplished
B. couldn’t have accomplished
C. were unable to accomplished
D. mustn’t have accomplished
答案：
A. shouldn’t have accomplished
(答案→)B. couldn’t have accomplished
C. were unable to accomplished
D. mustn’t have accomplished
解析：考查虚拟语气。句意：没有你的努力，我们不可能取得如此大的成功。谢谢你。“could+have+done”表示对过去事情的假设，意思是本来能够做某事而没有做。故选B。
