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