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': 'A synchronous cardioversion is given in \nSelect and explain. \nA. AF, B. Ventricular fibrillation, C. Atrial flutter, D. Ventricular tachycardia', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]