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
Commonly used type of radiation in radiotherapy is: 
Select and explain. 
A. Alpha rays, B. Beta rays, C. Gamma rays, D. X-rays
C: Gamma rays
Answer: C: Gamma rays 
Explanation: Ans. Gamma rays