The use of network（）,systems that effectively isolate an organization&39;s internal network structure from an（）network, such as the INTERNET is becoming increasingly popular. These firewall systems typically act as application-layer（）between networks, usually offering controlled TELNET, FTP, and SMTP access. With the emergence of more sophisticated（）layer protocols designed to facilitate global information discovery , there exists a need to provide a general （）for these protocols to transparently and securely traverse a firewall. A.safeguardsB.firewallsC.routersD.switches A.exteriorB.InternalC.centreD.middle A.hostsB.routersC.gatewaysD.officesA.networkB.sessionC.transmissionD.application A.frameworkB.internetworkC.computerD.application 请帮忙给出正确答案和分析，谢谢！
