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': 'Opaque porcelain: \nSelect and explain. \nA. is Feldspathic glass, B. contains opacifier like zirconium and titanium oxide, C. Not used to mask the colour of the cement used in placing of restoration, D. Used to produce the characteristic translucence, which is an inherent aspect of the incisal edge in natural teeth', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]