You want to implement a scheduler to process reporting algorithm. The report will not be shared and it will emailed to only root administrator.
A: Create a stateless session bean and register with the EJB timer service for time-based event notification.
C. Create a singleton session bean and register with the EJB timer service for time-based event notification.
The model answer : C.
But the answer should be A because there is a key word "the report will not shared". If a singleton is used as the model answer says, the variables in the singleton will be shared across the application and among different clients.