—— Do you still remember the day when we went to the Great Wall? —— I can’t remember it w

问题补充：

—— Do you still remember the day when we went to the Great Wall?

—— I can’t remember it well, but＿＿＿＿＿＿sometime last autumn?

A. might it be

B. could it have been

C. could it be

D. must it have been

答案：

A. might it be

(答案→)B. could it have been

C. could it be

D. must it have been

解析：could have done表示对过去发生情况的可能性推测。