— Do you still remember when we went to Chongqing? —I can’t remember now but sometime las

问题补充：

— Do you still remember when we went to Chongqing?

—I can’t remember now but sometime last summer?

A. could it be

B. might it be

C. could it have been

D. might it have been

答案：

A. could it be

B. might it be

(答案→)C. could it have been

D. might it have been

解析：could have done对过去的动作可能性的判断。