You are about to migrate a customer network to use a VSS. Which of these statements is true about a VSS？（）

• A、The VSS switch must be the root bridge for all VLANs and is automatically designated.
• B、The VSS switch is defined in RFC 4318 as a managed object.
• C、The PAgP+ or LACP protocols are used to maintain the operational state of the VSS devices.
• D、A VSS interoperates with a virtual port channel.
• E、The 802.1Q or ISL protocols are used to maintain the operational state of the VSS devices.
• F、A VSS increases the size of the spanning-tree domain.