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
Nowadays radium is not used in the Rx of cancer because: 
Select and explain. 
A. It decays faster and needs frequent replacement, B. It decays into daughter Radon which is a constant hazard, C. It has a very long half life, D. It is a very unstable element
B: It decays into daughter Radon which is a constant hazard
Answer: B: It decays into daughter Radon which is a constant hazard 
Explanation: Ans. It decays into daughter Radon which is a constant hazard