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': 'A 63-year-old woman develops exertional angina and has had two episodes of syncope. Examination shows a systolic ejection murmur with radiation to the carotids and a soft S2. Which of the following is the most likely diagnosis? \nSelect and explain. \nA. mitral stenosis, B. mitral insufficiency, C. aortic stenosis, D. aortic insufficiency', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Aortic stenosis is most likely to be associated with angina pectoris, syncope, and exertional dyspnea. Exertional syncope is caused by either systemic vasodilation in the presence of fixed or inadequate cardiac output, an arrhythmia, or both. Syncope at rest is most frequently a result of a transient ventricular tachyarrhythmia.', 'role': 'assistant'}]