This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Medicine
[{'content': '30-60deg left axis detion- \nSelect and explain. \nA. Left ventricular hyperophy, B. Right ventricular hyperophy, C. Aoic stenosis, D. Left atrial enlargement', 'role': 'user'}, {'content': 'Answer: A \nExplanation: High QRS voltage is the hallmark of left ventricular hyperophy(LVH), although many young patients have high QRS voltage without real LVH. Other associated hints (albeit nonspecific) are left axis detion, left atrial enlargement, widening of the QRS, and strain (associated ST-T abnormalities Ref Harrison 20th edition pg 1435', 'role': 'assistant'}]