Question

which reagent is used as a counterstain?
a) crystal violet
b) safranin
c) 95% ethyl alcohol
d) iodine

Explanation:

In Gram - staining, crystal violet is the primary stain. Iodine is the mordant. 95% ethyl alcohol is the decolorizer. Safranin is the counterstain which stains the Gram - negative bacteria (which have lost the crystal violet - iodine complex after decolorization) pink or red.

Answer:

B. Safranin