George, a 22-year-old mechanic, always seems to have a cloud over his head. For the past three weeks, he has had problems sleeping and he has little appetite or enjoyment of food. While he may sometimes seem to be relatively content for short periods of time, this happens very rarely and it never lasts for more than a week. If George were to seek help for his negative mood state, which of the following diagnoses would he most likely receive?
a. Adjustment disorder with depressed mood
b. Chronic adjustment disorder with depressed mood
c. Bipolar II
d. Major depressive disorder