Anthony's Performance Has Been Lower in the Last Six Months

Anthony's performance has been lower in the last six months than his average in the previous three years.Anthony's supervisor wants to understand if there are reasons within the organization's control that are causing Anthony's performance to slide.Anthony's job assignment has not changed,so the supervisor must consider all of the following factors EXCEPT

A) whether Anthony is having trouble working with new job software.
B) if Anthony's new co-workers are poor performers.
C) whether the supervisor herself has changed how she manages Anthony.
D) if Anthony's capabilities have changed.