You are answering a USMLE-style medical question. Question: A 33-year-old woman presents to the clinic for follow-up of her AIDS treatment with highly active anti-retroviral therapy (HAART). She is in good spirits and has been fully compliant with her medications and clinic visits. Other medications include prophylactic co-trimoxazole. Recent blood studies show the following: Hemoglobin (Hb%) 11 g/dL Mean corpuscular volume (MCV) 80 fl Reticulocyte count 0.5% Erythrocyte count 2 x 106/mm3 Leucocyte count 700/mm3 Neutrophils 40% Platelet count 20,000/mm3 Assays also show a decreased viral DNA and mRNA burden, as well as a significantly diminished viral load. To avoid modifying the effective anti-retroviral therapy, she is started on a ‘blood improving’ medication. Thirty minutes after the first dose, the patient develops difficulty breathing, severe muscle pain, and vomiting. Her pulse rate is 120/min and the blood pressure is 80/50 mm Hg. Which of the following medications was most likely administered to the patient? Options: A) Interleukin 3 B) Platelet-derived growth factor C) Sargramostim D) Thrombopoietin Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.