I really don’t know how to thank you , but for your help, I my lost necklace．
A. couldn’t have found
B. mustn’t have found
C. couldn’t find
D. wouldn’t find
网友回答
(答案→)A. couldn’t have found
B. mustn’t have found
C. couldn’t find
D. wouldn’t find
解析：考查虚拟语气。根据句中but for要不是，用虚拟语气，本题是对过去事实相反的虚拟语气，故用could have done，选A。