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
Which generation of flowable composites can be used as restorative material? 
Select and explain. 
A. 1st generation, B. 2nd generation, C. Both, D. None
B: 2nd generation
Answer: B: 2nd generation 
Explanation: Flowable composite
Low filler content, lower viscosity
1st generation:

Inferior mechanical properties
Only used as P&F sealant 
1st layer of composite on tooth surface

2nd generation:

Better mechanical properties
Can be used as restorative material
Entire restoration