Norby,an 18-Year-Old First-Year University Student,has Missed Almost All His Classes

Norby,an 18-year-old first-year university student,has missed almost all his classes during the past month.He spends most of his time in his bedroom,frequently not even bothering to get dressed or eat meals.He thinks his whole life has been a failure and blames himself for being a social misfit.Norby is most likely suffering from

A) major depressive disorder.
B) social anxiety disorder.
C) disruptive mood dysregulation disorder.
D) posttraumatic stress disorder.