A.When a single device is configured to provide differentiated services.
B.When multiple devices in a network are configured to use CoS to provide differentiated services.
C.When a device is used to connect to another autonomous system.
D.When CoS is used to classifiy traffic as low priority.

A.to use the classification to route traffic
B.to use the classification to reorder packets from various sources
C.to use the classification to discard malformed packets
D.to use the classification to provide the configured service level