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 heart on chest X–ray is formed by -a) Aortic archb) Left Pulmonary arteryc) Right atriumd) Left ventriclee) Right ventricle \nSelect and explain. \nA. b, B. c, C. ac, D. ad', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Amongst the given options, left heart border is formed by Aortic knuckle (formed by aortic arch) and left ventricle.\nSome guides have included left pulmonary artery in the answer. But, it is pulmonary trunk which forms left heart border (not left pulmonary artery).', 'role': 'assistant'}]