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: Unknown
[{'content': 'The right border of the heart is formed by - \nSelect and explain. \nA. Left Ventricle, B. Right Ventricle, C. Right Atrium, D. Left Atrium', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. is 'c' i.e., Right Atrium", 'role': 'assistant'}]