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: Dental
[{'content': 'Which of these is not a basic principle of radiation protection ? \nSelect and explain. \nA. Justification, B. Collimation, C. Limitation, D. Optimization', 'role': 'user'}, {'content': 'Answer: B \nExplanation: In addition to the three basic principles of radiation protection (justification, limitation, and optimization), one\xa0 can apply the following additional techniques to reduce the radiation burden to the patient:\n\nCollimation of the x-ray beam.\nCorrect focus-to-skin distance.\nLead apron with thyroid collar.\nMore radiation-sensitive image receptors.', 'role': 'assistant'}]