Someone knocked at the door in the middle of the night, but they hung up I could
来源：网络
时间：
推荐文章
Someone knocked at the door in the middle of the night, but they hung up ________ I could answer it．
A.as
B.since
C.until
D.before
试题答案
D
因从句中有could answer，可理解为“我还没来得及……”。