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 functional cusps are bevelled in the preparation of posterior cast crowns: \nSelect and explain. \nA. To reduce the stress at the line angles, B. To prevent the fracture of the tooth structure, C. For the structural durability of the restoration, D. To help in the retention', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]