This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Fundamentals in Radiology, Subject name: Radiology
[{'content': 'X-rays are modified - \nSelect and explain. \nA. Protons, B. Electrons, C. Neutrons, D. Positrons', 'role': 'user'}, {'content': 'Answer: B \nExplanation: X rays are the modified electrons from cathode striking the anode both are made up of tungsten which has a high melting point and low vapourisation pressure', 'role': 'assistant'}]