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': 'In PA view of X-ray chest, right border of the hea is formed by all except: \nSelect and explain. \nA. Superior venacava, B. Inferior venacava, C. Right atrium, D. Left atrial appendage', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. Left atrial appendage', 'role': 'assistant'}]