What can be done when VLANs need to span more than one switch? A$.$ No special mechanism is required.B$.$ Signaling is used between switches for each destination MAC address in the FDB to build the correct VLAN$-$to$-$MAC associations.C$.$ Signaling is used between switches for each source MAC address in the FDB to build the correct VLAN$-$to$-$MAC associations.D$.$ A VLAN tag is attached to the Ethernet frame to indicate VLAN membership. E$.$ It$$s not possible for VLANs to span more than one switch.