As he approached the door, Mike looked into the room again to see if he anything behind.
A. left
B. had left
C. has left
D. would leave
网友回答
A. left
(答案→)B. had left
C. has left
D. would leave
解析：B 考察动词时态。句意：当他快到门口的时候，麦克再一次看看房间是否落下什么东西。Leave behind所表示的动作发生在look into之前，因此使用过去完成时，表示在过去的某一时间或者某一动作之前就发生的动作。故B正确。