This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: NEET 2019, Subject name: Medicine
[{'content': 'Which wall of hea is enlarged first in a patient with mitral stenosis ? \nSelect and explain. \nA. Left atrium, B. Right atrium, C. Left ventricle, D. Right ventricle', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Wall of hea enlarged in mitral stenosis - left atria', 'role': 'assistant'}]