Question

—— 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

Answer 1

B

could have done表示对过去发生情况的可能性推测。