问题
选择题
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
答案
答案：A
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。
