You are answering a USMLE-style medical question. Question: A 21-year-old old college student is brought to the emergency department by his roommates because he has been "acting strangely." Over the last 7 months, he has claimed to hear voices telling him that he must prepare for the end of the world. He used to be a straight A student but started failing exams recently due to his erratic behavior. Furthermore, there are periods of time where he does not sleep for several days and redecorates the entire apartment. During those times he spends huge amounts of money on online shopping. These periods usually last for about 2 weeks and happen every other month. On physical exam, he appears unkept and irritated. He seems to respond to invisible stimuli, and he jumps from topic to topic without clear focus. Which of the following is most consistent with this patient's presentation? Options: A) Brief psychotic disorder B) Schizoaffective disorder C) Schizophreniform disorder D) Schizotypal personality disorder Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.