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: Anaesthesia
[{'content': 'Machine used noninvasively to monitor an external chest compression during cardiopulmonary resuscitation is \nSelect and explain. \nA. Zoll depth synchronizer, B. Zoll strength sensor, C. Zoll pAO2 monitor, D. Zoll AED -plus automatic external defibrillator', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]