You are configuring an 802.1Q trunk between a Layer 2 switch and a firewall. You read in the documentation that the best way to set up a trunk is to set the port as dynamic desirable. The trunk is not coming up. Which one of these options would be a valid explanation？ （）

• A、The firewall does not support Cisco Discovery Protocol. You should set the switchport trunk mode ON
• B、The firewall does not support Cisco Discovery Protocol. You should set the switchport trunk mode to OFF
• C、The firewall does not support Cisco Discovery Protocol. You should set the switchport trunk mode asauto.
• D、The firewall does not support DTP. You should set the switchport trunk mode to ON