You are answering a USMLE-style medical question. Question: A 4-year-old boy with acute lymphoblastic leukemia is admitted to the hospital to undergo allogeneic bone marrow transplantation. Two weeks after the conditioning regimen is started, he develops a temperature of 38.5°C (101.3°F). Laboratory studies show: Hemoglobin 8 g/dL Leukocyte count 1400/mm3 Segmented neutrophils 20% Eosinophils 0.5% Lymphocytes 87% Monocytes 1% Platelet count 110,000/mm3 Which of the following is the most appropriate pharmacotherapy for this patient?" Options: A) Transforming growth factor-β B) Erythropoietin C) Interleukin-5 D) Granulocyte-macrophage colony-stimulating factor Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.