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: Surgery
[{'content': 'Cryosurgery utilizes which of the following? \nSelect and explain. \nA. Nitrous oxide, B. Carbon dioxide, C. Liquid oxygen, D. Nitric dioxide', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]