On Cisco routers, how is hierarchical QoS implemented?

A.	Within the parent policy, reference another child policy using the policy-map command.
B.	Within the child policy, reference another parent policy using the policy-map command.
C.	Use the policy-map command within a service-policy to implement nested policy-maps.
D.	Within the parent policy-map, reference another child policy-map using the service-policy command.