To provide firewall traversal, which components are needed?

To provide firewall traversal, which components are needed?

A.
2 Cisco TelePresence Video Communication Server Expressways

B.
1 Cisco TelePresence Video Communication Server Control and 1 Cisco TelePresenceVideo Communication Server Expressway

C.
2 Cisco TelePresence Video Communication Server Controls

D.
1 Cisco TelePresence Video Communication Server Control and 2 CiscoTelePresence Video Communication Server Expressways