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
Element most commonly used in brachytherapy of carcinoma cervix: March 2005 
Select and explain. 
A. Carbon, B. Technetium, C. Nitrogen, D. Cesium
D: Cesium
Answer: D: Cesium 
Explanation: Ans. D: Cesium