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 secondary flare is necessary for class II cast gold inlay preparation for several reasons, but basically the direction of the flare results in: \nSelect and explain. \nA. Good aesthetics, B. 60° marginal metal which is burnishable, C. 40° marginal metal which is burnishable, D. 10° marginal metal which is burnishable', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Secondary flare:\nIt is a flat plane superimposed peripherally to the primary flare. Advantages are:\n\nSecondary flare ensures cavosurface margins to extend into embrasures (self-cleansing area).\nPermits easy burnishing and finishing of the restoration.\nProduces more obtuse-angled and stronger cavosurface margin.\n\nIn class II cast gold inlay, proximal box should have flares so as to have the metal of 30-40° which is burnishable.', 'role': 'assistant'}]