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': 'Right heart border is mainly formed by \nSelect and explain. \nA. Right atrium, B. Superior vena cava, C. Right ventricle, D. Inferior vena cava', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Right heart border: SVC, Rightatrium, Ivc mainly by Right atrium.', 'role': 'assistant'}]