Years after he barely survived a terrorist attack that killed his wife and two children, Mr. Puskari suffers recurring flashbacks and frequent nightmares of the event that render him incapable of holding a steady job. Mr. Puskari is most clearly showing signs of: 

A.  obsessive-compulsive disorder.

B.  generalized anxiety disorder.

C.  post-traumatic stress disorder.

D. dysthymic disorder.