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 first layer of porcelain applied on to a metal in PFM crowns would be \nSelect and explain. \nA. Opaque, B. Body, C. Incisal, D. Both 1 and 2', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]