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.