You are answering a USMLE-style medical question. Question: A newborn is found to be extremely cyanotic immediately after birth. He then develops progressive respiratory failure and is admitted to the neonatal ICU. A single loud S2 heart sound is appreciated as well as a machine-like murmur at the left upper sternal border. Radiography shows an enlarged "egg-shaped" heart. The newborn is then taken for a atrial septostomy to alleviate the condition pending definitive surgical correction. Which of the following is the most likely cause of this newborn's condition? Options: A) Coarctation of the aorta B) Persistent truncus arteriosus C) Transposition of great vessels D) Tricuspid atresia Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.