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
[{'content': 'Most commonly used colour of the filter used in dark\nroom safelight is: \nSelect and explain. \nA. Blue, B. Red, C. Green, D. Yellow', 'role': 'user'}, {'content': "Answer: B \nExplanation: X-ray\xa0 films\xa0 are\xa0 very\xa0 sensitive\xa0 to\xa0 the\xa0 blue-green\xa0 region\xa0 of\xa0 the spectrum and are less sensitive to red wavelengths. The red GBX-2 filter is recommended as a safelight in darkrooms where either intraoral or extraoral films are handled because this filter transmits light only at the red end of the spectrum.\nFilm handling under a safelight should be limited to about 5 minutes because film emulsion shows some sensitivity to light from a safelight with prolonged exposure. The older ML-2 filters (yellow light) are not appropriate for fast intraoral dental film or extraoral panoramic or cephalometric film.\n\xa0\nReference: White and Pharoah's Oral Radiology Principles and Interpretation 7th edition page no 71", 'role': 'assistant'}]