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 most common mechanical failure for metal-ceramic restorations is \nSelect and explain. \nA. Debonding of the porcelain from the metal., B. Shrinkage of the porcelain at mouth temperature., C. Debonding of the PFM from the tooth., D. None of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]