Which statement about best carmine staining is true?

• A. Ammonia maintains the high pH in the staining solution
• B. Absolute alcohol is a decolorizer
• C. Best carmine is more specific than PAS
• D. Nuclei stain pink

Answer: (A)

Best carmine staining relies on an alkaline environment to make the dye bind specifically to nuclear material. Ammonia is added to the staining solution to raise and maintain the high pH, which drives the dye to bind to chromatin and gives nuclei a bright red to magenta color with minimal background. This makes the statement about ammonia maintaining the high pH the true one. In contrast, absolute alcohol isn’t used as a decolorizer in this method, Best carmine targets nuclei rather than being more specific than PAS (which stains carbohydrates and mucosubstances), and nuclei do not stain pink with this stain (they appear deep red/magenta).