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': 'In which of the following types of cardiac arrest is DC counter shock the only definitive treatment? \nSelect and explain. \nA. Asystole, B. Electromechanical dissociation, C. Ventricular fibrillation, D. All of the above', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]