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
Microfilled composites cannot have a high filler load due to: 
Select and explain. 
A. Small size of filler particles which decreases  the overall matrix, B. More surface area per unit volume, C. Low modulus of elasticity, D. Wear of opposing tooth structure caused by microfillers
B: More surface area per unit volume
Answer: B: More surface area per unit volume 
Explanation: Filler content of microfilled composite  is 50-60% by weight. Because of the greater surface area per unit volume of these microfine particles they cannot be heavily filled.
Reference- Sturdevant 6th ed P:218