Problem: A 16-year-old boy with schizophrenia is treated with several antipsychotic drugs without an adequate response. He is started on a new drug and, within 1 month, presents with pneumonia and a cough. Workup reveals a low white blood cell count with an absolute neutrophil count less than 800/mm^3. On what drug was he most likely started? A. Amantadine B. Clozapine C. Chlorpromazine D. Haloperidol