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 one of the following is most elastic? 
Select and explain. 
A. α titanium, B. β titanium, C. Chrome-cobalt-nickel, D. Nickel titanium
D: Nickel titanium
Answer: D: Nickel titanium 
Explanation: None