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
The most important cause for marginal failure of amalgam restoration is: 
Select and explain. 
A. Increased creep, B. Decreased strength, C. Tarnish and corrosion, D. Delayed setting of the material
A: Increased creep
Answer: A: Increased creep 
Explanation: None