局内投交的特快专递邮件，自第1次发出（）之日起满12天仍无人领取，按无法投递邮件处理。
A.通知单
B.详情单
C.催领单
D.通知签条
参考答案：A
Peter could hardly see the words on the blackboard, ________?
A．did he
B．couldn't he
C．didn't he
D．could he
