【题目】By the time I locked the door, I realized I ______my keys at home.
A. had described B. had explained
C. had forgotten D. had left
在线课程【答案】D
【解析】句意为截止到我锁门的时候，我意识到我把钥匙拉家里了。By the time 主句用过去完成时。A. had described 描述 B. had explained解释 C. had forgotten忘记 D. had left落下