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
An example of a isotope that is predominantly a beta emitter is 
Select and explain. 
A. 125 Iodine, B. 32 Phosphorus, C. 51 Chromium, D. 99m Technetium
B: 32 Phosphorus
Answer: B: 32 Phosphorus 
Explanation: None