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 provide opacity to composite? \nSelect and explain. \nA. TEGDMA, B. BIS-GMA, C. TiO2, D. None', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]