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 side of mediastinum shadow is not formed by: \nSelect and explain. \nA. Superior venacava, B. Right innominates, C. Right atrium, D. Right ventricle', 'role': 'user'}, {'content': 'Answer: D \nExplanation: D i.e. Right ventricle', 'role': 'assistant'}]