Application Level Firewalls are commonly a host computer running proxy server software, which
makes a?

A.
Proxy Client

B.
Proxy Session

C.
Proxy System

D.
Proxy Server

Explanation:
A proxy server is a server that sits between a client and server application, such as a Web browser
and a source web server. It intercepts all requests to the real server to see if it can fulfill the requests
itself. If not, it forwards the request to the original source web server. Firewalls usually provides this
kind of services to have more control over user request and allow / deny the traffic of those through
the gateway. At this time the most common Proxy server is for HTTP protocol, we can also have
proxies for SMTP and FTP.