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 percentage of copper in high copper alloy is: 
Select and explain. 
A. 10-12%, B. 0 -6%, C. 13-30%, D. 20 -30%
C: 13-30%
Answer: C: 13-30% 
Explanation: None