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 is the only nearly pure metal used for dental casting purposes? 
Select and explain. 
A. Gold, B. Palladium, C. Silver, D. Pure titanium CP Ti
D: Pure titanium CP Ti
Answer: D: Pure titanium CP Ti 
Explanation: CP titanium, which is classified in four different grades, can technically be considered as an alloy because small percentages of other impurity elements are allowed as specified by a standard that has been established by the American Society for Testing and Materials (ASTM) for each grade. Although it is classified as commercially pure, grade 2 CP-Ti may contain up to 0.10% C, 0.30% Fe, 0.015% H, 0.03% N, 0.25% O, and 0.40% of other elements.
Phillips 12th edition page 71