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
Secondary flare provides a marginal metal of: 
Select and explain. 
A. 10-20 degrees, B. 30-40 degrees, C. 140-150 degrees, D. None of the above
B: 30-40 degrees
Answer: B: 30-40 degrees 
Explanation: Secondary flare:
It is a flat plane superimposed peripherally to the primary flare. Advantages are:

Secondary flare ensures cavosurface margins to extend into embrasures (self-cleansing area).
Permits easy burnishing and finishing of the restoration.
Produces more obtuse-angled and stronger cavosurface margin.

In class II cast gold inlay, proximal box should have flares so as to have metal of 30-40° which is burnishable.