单选题 We ______ our dinner when a policeman came to the door.
A. just had B. have just had C. just have had D. had just had

【正确答案】 D
【答案解析】当警察到门口的时候我们刚吃完饭。根据主句动作比从句动作早发生，因此时态比从句要早，是过去的过去，所以选过去完成式。