What are two main purposes of QoS marking? (Choose two)

A.
To sort traffic into different service classes for QoS treatment.

B.
To signal network devices on which QoS mechanism should be employed to meet the requirements of a particular service class.

C.
To set fields in IP packets and identify that packet as belonging to a specific class of service.

D.
To allow edge devices to select the QoS level on an application-by-application basis.