A 33- year- old man presents to a psychiatrist with concern about his excessive hand washing. He reports that he has a ritualistic washing routine that takes at least 20 minutes, which he performs multiple times per day for fear of contamination with infectious disease. When further interviewed, he states that he has recurrent and persistent thoughts about hand washing and risk of contamination, which he tries unsuccessfully to suppress. He reports an overwhelming sense of anxiety if he does not wash his hands or if he does not complete the "ritual". He says the behavior is "out of control". He recognizes these thoughts as functions of his own mind. He has no other symptoms. What is the likely diagnosis?

A. Obsessive- compulsive disorder.
B. Obsessive- compulsive personality disorder.
C. Schizophrenia
D. Specific phobia.