A 19- year- old college freshman wears a wizard hat every day around campus. When asked why, he tells people it is because "the hat helps me think better." He has had few friends but enjoys participating in medieval role- playing games. He earns excellent grades in class and grooms himself appropriately every day. His speech is fluent. His thought process is linear, although he perseverates on various wizard spells he has learned online. His affect is restricted. He denies any hallucinations or any changes in sleep, mood, appetitie, or energy. His unusual "style" has interfered with his getting a job, which he needs to remain in school. What is the likely diagnosis?
A. Bipolar I disorder.
B. Schizoaffective disorder.
C. Schizophrenia
D. Schizotypal personality disorder.