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': "Which of the following doesn't form the right side of the mediastinal shadow? \nSelect and explain. \nA. Superior venacava, B. Right innominate vessels, C. Right border of atrium, D. Right ventricle", 'role': 'user'}, {'content': 'Answer: D \nExplanation: Right ventricle forms the anterior border of hea.', 'role': 'assistant'}]