问题
选择题
— Do you still remember when we went to Nanjing?
— I can't remember now but ________sometime last summer?
A．might it be
B．could it be
C．could it have been
D．should it have been
答案
C
情态动词加现在完成式，表示对过去的推测，could表可能性，should表过去该做而没做的事。