This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Physics of Radiotherapy, Subject name: Radiology
[{'content': 'Maximum penetrating rays: \nSelect and explain. \nA. Alpha, B. Beta, C. Gamma, D. Delta', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. (c) GammaRef.: Essentials of radiological Science 2nd ed. /10* Maximum penetrating is gamma rays, therefore least dangerous. Hence gamma camera is used therapeutically for myocardial perfusion imaging.* Least penetrating is alpha rays, therefore most dangerous', 'role': 'assistant'}]