In the switching network as shown in the figure, all three switches have only default VLAN1, the interconnection ports of the three switches are Trunk, and all VLANs are allowed to pass, and the three switches have the global and port GVRP functions enabled. VLAN 10 is created on the switch SWA, VLAN 20 is created on the switch SWC, and the GVRP registration mode of the Ethernet 1/0/1 port is set to Forbidden on the switch SWA, and the display vlan SWC is executed on the SWC. The existing VLANs on SWC are available (choose one or Multiple)

Regarding the basic concepts of MSTP, the correct statement is

Regarding the MSTP BPDU format, the correct statement is

The IP address of the host PCA is 40.1.1.1, the MAC address is 0011.1111.1111, and it is connected to the GigabitEthernet1/0/1 port of the switch SWA. The following commands are configured on the switch SWA:
[SWA]vlan 10
[SWA-vlan10]quit
[SWA]vlan 20
[SWA-vlan20]protocol-vlan ipv4
[SWA-vlan20]quit
[SWA]vlan 30
[SWA-vlan30]quit
[SWA]mac-vlan mac-address 0011-1111-1111 vlan 30
[SWA]vlan 40
[SWA-vlan40]ip-subnet-vlan ip 50.1.1.0 255.255.255.0
[SWA-vlan40]quit
[SWA]interface GigabitEthernet 1/0/1
[SWA-GigabitEthernet1/0/1]port link-type hybrid
[SWA-GigabitEthernet1/0/1]port hybrid pvid vlan 10
[SWA-GigabitEthernet1/0/1]port hybrid vlan 10 20 30 40 untagged
[SWA-GigabitEthernet1/0/1]port hybrid protocol-vlan vlan 20 0
[SWA-GigabitEthernet1/0/1]port hybrid ip-subnet-vlan vlan 40
[SWA-GigabitEthernet1/0/1]mac-vlan enable
[SWA-GigabitEthernet1/0/1]vlan precedence ip-subnet-vlan
After the configuration is complete, it can be judged that PCA will join

As shown in the networking, SWA and SWB enable STP, SWC does not enable STP when initially Link 2 is not connected, PCB can send data to PCA, if Link 1 fails at this time, the maintenance personnel will connect Link 2, then The statement about the recovery process from PCB to PCA data transfer industry is correct (assuming PCA will not actively send data) __