Which Statements About QinQ Are True? (Choose Two.)

Which statements about QinQ are true? (Choose two.)

A) QinQ saves VLANs on the public network.
B) To avoid VLAN conflict, the customer must negotiate with the service provider before modifying the VLANs on its private network.
C) When the service provider upgrades the network, the configurations on the user network do not need to be modified.
D) All of the above