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 X-ray right border of mediastinum is formed by all EXCEPT \nSelect and explain. \nA. SVC, B. Right atrium, C. Right ventricle, D. Right brachiocephalic veins', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Right mediastinal border is formed by right innominate (brachiocephalic) vein, SVC, right atrium, and IVC (IVC may not be visible in PA view).', 'role': 'assistant'}]