A.It is used to validate the sources of VTP advertisements sent between switches.
B.It is used to access the VTP server to make changes to the VTP configuration.
C.It allows two VTP servers to exist in the same domain， each configured with different passwords.
D.It is the password required when promoting a switch from VTP client mode to VTP server mode.
E.It is used to prevent a switch newly added to the network from sending incorrect VLAN information to the other switches in the domain.

A.to verify the type of cable interconnecting two devices
B.to determine the status of network services on a remote device
C.to obtain VLAN information from directly connected switches
D.to verify Layer 2 connectivity between two devices when Layer 3 fails
E.to obtain the IP address of a connected device in order to telnet to the device
F.to determine the status of the routing protocols between directly connected routers