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: Dental
[{'content': 'The best fuel gas when used with oxygen is: \nSelect and explain. \nA. Hydrogen, B. Natural gas, C. Propane, D. Acetylene', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Propane\nOf the fuel gases, the best choice is propane. Butane, which is more readily available in some parts of the\xa0world, has a similar flame temperature and heat content as propane.\xa0Both\xa0 propane\xa0 and\xa0 butane\xa0have\xa0the\xa0advantage\xa0of\xa0being relatively pure compounds; therefore, they are uniform in quality are virtually water-free, and burn cleanly (provided\xa0that the torch flame is properly adjusted).', 'role': 'assistant'}]