This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Radiotherapy, Subject name: Radiology
[{'content': 'Direct action of radiation is the dominant process for \nSelect and explain. \nA. X-rays, B. Neutrons and alpha paicles, C. Electrons, D. Gamma rays', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ionizing radiation acts by two methods: Direct and IndirectDirect action is radiation directly causing DNA damage; example: neutrons and alpha paiclesIndirect action is radiation causing free radical production which acts on DNA; example: photons and gamma raysReference: Khan Physics of Radiation therapy; 5th edition', 'role': 'assistant'}]