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 of the following properties is the most trouble some for composite materials used for posterior restorations? 
Select and explain. 
A. Wear resistance, B. Water sorption, C. Coefficient of thermal expansion, D. Compressive strength
A: Wear resistance
Answer: A: Wear resistance 
Explanation: None