When deploying it behind a firewall, which three items must be configured on the firewall to permit communication through to it? (Choose three

The Cisco GSS serves as an authoritative name server for one or more domains. When deploying it behind a firewall, which three items must be configured on the firewall to permit communication through to it? (Choose three.)

A.
CDP messages

B.
DNS queries

C.
other protocols (FTP, Telnet, SSH, SNMP)

D.
keepalive protocol (KAL-AP, ICMP, HTTP, and user defined TCP ports)