国家开放大学 / 综合英语（2）
—Are you ready? I’m coming.
—Oh, I’m sorry to let you _ _ _ _ _ _ , but I’ve just received an urgent task.
a.off
b.back
c. against
d.down
—Oh, I’m sorry to let you _ _ _ _ _ _ , but I’ve just received an urgent task.
a.off
b.back
c. against
d.down
参考答案：
佳题速递：