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
[{'content': 'The principle used in radiotherapy is: \nSelect and explain. \nA. Cytoplasmic coagulation, B. Ionising the molecules, C. DNA damage, D. Low dose causes tissue necrosis', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. DNA damage', 'role': 'assistant'}]