A critical function of a firewall is to act as a:

A.
special router that connects the Internet to a LAN.

B.
device for preventing authorized users from accessing the LAN.

C.
server used to connect authorized users to private trusted network resources.

D.
proxy server to increase the speed of access to authorized users.

Explanation:
A firewall is a set of related programs, located at a network gateway server, that protects the resources of a
private network from users of other networks. An enterprise with an intranet that allows its workers access to
the wider Internet installs a firewall to prevent outsiders from accessing its own private data resources and for
controlling the outside resources to which its own users have access. Basically, a firewall, working closely with
a router program, filters all network packets to determine whether or not to forward them toward their
destination. A firewall includes or works with a proxy server that makes network requests on behalf of
workstation users. A firewall is often installed in a specially designated computer separate from the rest of the
network so no incoming request can get directed to private network resources.