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': 'Left border of hea on chest X-ray is formed by: \nSelect and explain. \nA. Aoic arch, B. Left Pulmonary aery, C. Left ventricle, D. All', 'role': 'user'}, {'content': 'Answer: D \nExplanation: A i.e. Aoic arch; C i.e. Left ventricle; B i.e. Left Pulmonary aery', 'role': 'assistant'}]