You have created a resource plan， DB_PLAN， using DBMS_RESOURCE_MANAGER.CREATE_SIMPLE_PLAN and you want to impose a restriction on utilization of resources by the database users.   Which step must be performed before you can start using the resource plan？（）

• A、assign users to consumer groups
• B、set the resource plan for the instance
• C、configure a simple resource plan and specify plan directives
• D、configure a complex resource plan and specify plan directives