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 retention in the cast metal restoration is mainly by: \nSelect and explain. \nA. Diverging vertical walls, B. Parallel vertical walls, C. Luting cement, D. All of the above', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Cast-metal intracoronal restorations, referred to as inlay restorations, rely on diverging vertical walls that are almost parallel and a luting cement to provide retention of the casting in the tooth.\nSturdevant operative dentistry\xa07th Edition, Page No:120', 'role': 'assistant'}]