遗失物自发布招领公告之日起（）个月内无人认领，归国家所有。
A、3
B、6
C、9
D、10
参考答案：B
A firewall is a (68) system designed to (69) all organization, s network against threats.
A．prevent
B．protect
C．develop
D．exploit
顶升作业过程中须将回转制动器锁住防止顶升转动。
