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': 'The right side of mediastinum shadow is not formed by: \nSelect and explain. \nA. Superior vena cava, B. Right innominate vein, C. Right atrium, D. Right ventricle', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. Right ventricle', 'role': 'assistant'}]