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': 'All of the following features can differentiate between ventricular tachycardia and supraventricular tachycardia EXCEPT \nSelect and explain. \nA. QRs < 0.14 seconds, B. Ventricular rate > 160/min, C. Variable first heart sound, D. Relieved by carotid sinus massage', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]