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 cohesion of direct gold filling at room temperature
is an example of: 
Select and explain. 
A. Wedging, B. Annealing, C. Adaptability, D. Atomic attraction
D: Atomic attraction
Answer: D: Atomic attraction 
Explanation: None