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: Radiology
Which of the following is not an aificial radio isotope element? 
Select and explain. 
A. CO 60, B. 1-125, C. Ra226, D. CO59
D: CO59
Answer: D: CO59 
Explanation: Ans. CO59