This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: M.I. & Angina, Subject name: Medicine
[{'content': 'ECG of a patient had ST segment elevation in VI-V6, lead I and aVL. Which of the following branches is involved? \nSelect and explain. \nA. Left main coronary artery, B. Left anterior descending, C. Diagonal 1 branch of LAD, D. Septal branch of LAD', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. (a) Left main coronary artery.', 'role': 'assistant'}]