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
SI unit of Radioactivity is 
Select and explain. 
A. Curie, B. Becquerel, C. Roentgen, D. Sievert
B: Becquerel
Answer: B: Becquerel 
Explanation: SI unit - Becquerel
Old unit - Curie