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': 'All of the following procedures are recommended in dark\nroom processing except: \nSelect and explain. \nA. Use of high intensity and short wavelength light (Red), B. Light is placed 4 feet above the processing tank, C. Light is placed behind the processing tank, D. X-ray of red filter GBX-2 is used', 'role': 'user'}, {'content': "Answer: A \nExplanation: One of the most important requirements is that the darkroom be lightproof. If it is not, stray light can cause film fogging and loss of contrast. To make the darkroom lightproof, a light-tight door or doorless maze (if space permits) is used.\nSAFELIGHTING\nThe processing room should have both white illumination and safelighting. Safelighting is low-intensity illumination of relatively long wavelength (red) that does not rapidly affect open film but permits one to see well enough to work in the area. To minimize the fogging effect of prolonged exposure, the safelight should have a frosted 15-watt bulb or a clear 7.5-watt bulb and should be mounted at least 4 feet above the surface where opened films are handled.\nX-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. Film 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\xa0Reference: White and Pharoah's Oral Radiology Principles and Interpretation 7th edition page no 70, 71", 'role': 'assistant'}]