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: Medicine
[{'content': 'Water hammer pulse seen in - \nSelect and explain. \nA. Aortic stenosis, B. Aortic regurgitation, C. Aortic stenosis and Aortic regurgitation, D. Mitral regurgitation', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]