Which statement is true while creating subplans using Resource Manager?

Which statement is true while creating subplans using Resource Manager?

A.
The subplan must belong to the consumer group, SYS_GROUP.

B.
The total CPU usage at any given level must be less than 100%.

C.
The subplans can be used to restrict the degree of parallelism for a user.

D.
You can use a resource plan instead of a consumer group to implement a priority ranking within the plan.