The Nurse Manager of a Unit Was Demoted to Staff

The nurse manager of a unit was demoted to staff nurse 6 months ago.Because of being near retirement,the former nurse manager wanted to be employed at the hospital and was offered a position on the same unit.The former nurse manager complains often about how infrequently the current nurse manager is available on the unit and argues with physicians and co-workers.Patients have complained about the attitude of the former nurse manager.The behaviour of the former nurse manager can be best explained as being caused by

A) overwork in the staff nurse position.
B) inadequate mentoring in the new role.
C) anger as a stage of the grieving process.
D) demotion as a threat to personal identity.