A 55- year- old woman presents to the hospital for treatment of acute myeloid leukemia, which was diagnosed 1 month ago. Her husband passed away 1 year ago from a cancer that he had battled for 3 years. She reports seeing a therapist for the "past couple of years" while dealing wit her husband's illness and death. Her primary care team noted that she is frequently tearful in the hospital and looked relieved when a psychiatric evaluation was suggested. On interview, she reports feeling sad much of the day but that she is trying to stay upbeat about her treatment. She also reports feelings of hopelessness. Her appetite and sleep have been poor, and she has lost 50 pounds since the death of her husband. She feels guilty- "I wish I had taken better care of my husband in the end". She reports feeling isolated from friends and family as well. She makes a vague complaint of anxiety, which "comes and goes" throughout the day and is being treated with a round- the- clock schedule of benzodiazepines. She says that she "does not care if cancer kills her too". What is the likely diagnosis?

A. Adjustment disorder.
B. Generalized anxiety disorder.
C. Major depressive disorder.
D. Uncomplicated bereavement.