You need to add VLAN 4 to the allowed list on a trunk interface. Currently VLANs 5 through 8 are allowed. Which command will add only this VLAN without interruption to the network?

A. Switch(config-if)# switchport trunk allowed vlan add 4
B. Switch(config-if)# add allowed vlan 4
C. Switch(config-if)# switchport trunk add vlan 4
D. Switch(config-if)# switchport trunk allowed add vlan 4

A. The command switchport trunk allowed vlan add 4 will add VLAN 4 to the existing list of VLANs already allowed on the interface.