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 main disadvantage of metal ceramic restoration as\ncompared to porcelain jacket crown is \nSelect and explain. \nA. Less strength, B. Poor colour matching, C. More porous, D. Less retentive', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]