Basically, a firewall is a (71) process or a set of integrated processes that runs on a router or (72) to control the flow of networked application traffic (73) through it. Typically, firewalls are placed on the entry point to a (74) Network such as the Internet. They could be considered traffic cops. The firewall’s (75) is to ensure that all communication between an organization’s network and the Internet conform to the organization’s security policies.

（74）处填（）。

A．local

B．national

C．private

D．public

下列细胞中哪种细胞是上皮根鞘断裂后的残留（）

A.缩余釉上皮

B.Serre上皮剩余

C.Malassez上皮剩余

D.牙板

E.上皮隔