Question

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

Answer 1

B

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。