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
Metallic oxides are added in porcelain to: 
Select and explain. 
A. Increase strength, B. Provide color, C. Improve bonding with metal, D. All of the above
B: Provide color
Answer: B: Provide color 
Explanation: None