You are answering a USMLE-style medical question. Question: A 3-week-old male newborn is brought to the hospital because of poor weight gain since birth. He was born at 38 weeks' gestation via normal vaginal delivery. He weighed 3005 g (6 lb, 10 oz) at birth and currently weighs 2835 g (6 lb, 4 oz). He has been latching on and breastfeeding well since birth. His mother has a history of Graves' disease and underwent near-total thyroidectomy in the second trimester of her pregnancy after her symptoms could not be controlled with antithyroid drugs. She is currently receiving L-thyroxine therapy. The patient's temperature is 38.9°C (102°F), pulse is 176/min, and respirations are 42/min. He appears irritable. Examination shows a diaphoretic infant with a paucity of subcutaneous fat. There is swelling of the neck at the midline. Which of the following is the most likely cause? Options: A) Transplacental passage of thyroid peroxidase antibodies B) Transplacental passage of TSH receptor antibodies C) Transplacental viral infection D) Opiate use in the mother Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.