If you met someone in January and she was severely depressed, what is one way you might determine if her depression was due to seasonal affective disorder, or to some other form of depression?

A) Ask her if she attributes her successes to internal or external forces.
B) Ask her if she attributes her failures to stable, global, and internal factors.
C) Determine if exposure to bright lights for a few hours each day helps alleviate her depression.
D) Have psychiatrists rate the severity of the depression.