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
Aificial radioisotops: 
Select and explain. 
A. Radium, B. Uranium, C. Plutonium, D. Iridium
D: Iridium
Answer: D: Iridium 
Explanation: D i.e. Iridium