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
In facial porcelain inlay what should be kept in mind? 
Select and explain. 
A. Facial surface should be perpendicular to cavity margins, B. Facial surface should converge to cavity margins, C. Facial surface should be parallel to cavity margins, D. Axial wall is 2.5 mm deeper than normal
A: Facial surface should be perpendicular to cavity margins
Answer: A: Facial surface should be perpendicular to cavity margins 
Explanation: None