The Database Resource Manager is not currently active in your database that is up and running. You created a resource plan named DAY_PLAN that contains two sub-plans named MANAGERS_PLAN and CLERKS_PLAN. You decided to activate DAY_PLAN by executing the following statement：       SQL>ALTER SYSTEM SET RESOURCE_MANAGER_PLAN = ’managers_plan’；  What will be the outcome of this statement？（）  

• A、 The statement will deactivate DAY_PLAN.
• B、 The statement will activate DAY_PLAN as the top plan.
• C、 The statement will activate MANAGERS_PLAN as the top plan.
• D、 The statement will return an error because MANAGERS_PLAN is not the top plan.