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
Radio opacity to composite resins is rendered by 
Select and explain. 
A. Silica glass, B. Organic matrix, C. Barium glass and strontium glasses, D. Fluoride particles
C: Barium glass and strontium glasses
Answer: C: Barium glass and strontium glasses 
Explanation: None