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': 'Which of the following material used in orthodontics, commonly causes sensitivity \nSelect and explain. \nA. Steel, B. Ceramic, C. Nickel, D. Plastic', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]