I could have called you for help but I your number.A. couldn’t rememberB. didn’t rememb

问题补充：

I could have called you for help, but I your number.

A. couldn’t remember

B. didn’t remember

C. should have remembered

D. hadn’t remembered

答案：

A. couldn’t remember

(答案→)B. didn’t remember

C. should have remembered

D. hadn’t remembered

解析： could have done 表示过去本可以做某事而没有，是一个与过去事实相反的虚拟语气，but后引出了一个过去事实,说明不能做的理由。故remember用一般过去时。