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': 'A 40 year old male patient came for routine dental checkup. Patient gives history of root canal treatment with 17 and 27 done using excimer. This type of lasers are: \nSelect and explain. \nA. Special infrared lasers\u200b, B. Special ultraviolet lasers\u200b, C. Special visible light lasers, D. Special blue light lasers\u200b  \u200b', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The lasers range from long wavelengths (infrared), through visible wavelengths, to short wavelengths\u200b (ultraviolet). Excimers are special ultraviolet lasers.\u200b', 'role': 'assistant'}]