This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Radiology
[{'content': 'Not a sign of Right atrial enlargement: \nSelect and explain. \nA. Prominent right heart border with increased convexity (PA view), B. Prominent anterosuperior part of cardiac shadow (lateral view), C. Obliteration of retrosternal clear space (Lateral view), D. Haffman-Rigler Sign (Lateral view)', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Haffman-Rigler sign - Horizontal distance of greater than 1.8cm between posterior aspect of IVC and Posterior border of heart - Sign of Left Ventricular enlargement.', 'role': 'assistant'}]