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
All may be used in interstitial brachytherapy except 
Select and explain. 
A. Cs137, B. Au192, C. Ir192, D. Co60
D: Co60
Answer: D: Co60 
Explanation: D i.e. C060