You are answering a USMLE-style medical question. Question: A 6-year-old African American boy is referred to the hospital by his family physician for jaundice, normocytic anemia, and severe bone pain. He has a history of several episodes of mild bone pain in the past treated with over the counter analgesics. On physical examination, the child is icteric with nonspecific pain in his hands. His hands are swollen, tender, and warm. There is no chest pain, abdominal pain, fever, or hematuria. A complete metabolic panel and complete blood count with manual differential are performed: Total bilirubin 8.4 mg/dL WBC 9,800/mm3 Hemoglobin 6.5 g/dL MCV 82.3 fL Platelet count 465,000/mm3 Reticulocyte 7% Peripheral blood smear shows multiple clumps of elongated and curved cells and erythrocytes with nuclear remnant. The patient's hemoglobin electrophoresis result is pictured below. What is the most likely cause of his condition? Options: A) Sickle cell trait B) Sickle cell disease C) Hemoglobin F D) HbC Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.