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 walls of full gold crown preparation should: \nSelect and explain. \nA. Be parallel, B. Angle of convergence 5°, C. Angle of divergence 5°, D. Roughened to increase retention', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]