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
The principle used in radiotherapy is: 
Select and explain. 
A. Cytoplasmic coagulation, B. Ionising the molecules, C. DNA damage, D. Low dose causes tissue necrosis
C: DNA damage
Answer: C: DNA damage 
Explanation: Ans. DNA damage