I really dont know how to thank you but for your help I my lost necklace.A. couldnt

问题补充：

I really don know how to thank you, but for your help, I my lost necklace.

A. couldn have found

B. mustn have found

C. couldn find

D. wouldn find

答案：

(答案→)A. couldn have found

B. mustn have found

C. couldn find

D. wouldn find

解析：A句意：我真的不知道该怎样感谢你，没有你的帮助，我不可能找到我丢失的项链。couldn have done表示对过去情况的否定推测，意为“不可能”。