Sean Describes Himself as Having Hardly Ever Been Happy

Sean describes himself as having hardly ever been happy. He occasionally feels okay, but it never lasts more than a day or so. He has trouble sleeping, doesn't eat much, and feels like nothing will ever change in his life. He says this has been going on for as long as he can remember. The best diagnosis for Sean is

A) cyclothymia.
B) dysthymia.
C) major depressive disorder.
D) bipolar II.