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