高等继续教育 / 电子商务英语
正确率：100%
题型描述: 单选题
I knocked at the door several times ＿＿＿＿＿＿ an elderly lady came to answer it.
A.then
B.before
C.unless
D.after
I knocked at the door several times ＿＿＿＿＿＿ an elderly lady came to answer it.
A.then
B.before
C.unless
D.after
参考答案：
佳题速递：