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
Principles used in Radio Therapy is: 
Select and explain. 
A. Infrared rays, B. Ionizing molecules, C. Charring of nucleoprotein, D. Ultrasonic effect
B: Ionizing molecules
Answer: B: Ionizing molecules 
Explanation: B i.e. Ionizing molecules