You notice that a job in a chain has not completed on a nonconstrained RAC database. Which of these are valid reasons why that might occur？（）  

• A、 The job priority is 1 and the resource consumer group CPU emphasis allocation is a low percentage.
• B、 The job affinity is to a service and one node in that service is unavailable.
• C、 The job affinity is to an instance and that instance is unavailable.
• D、 There is no service affinity.
• E、 None of the above.