What is the primary difference between gram-positive and gram-negative bacteria in terms of their staining patterns? Select one: a. Gram-positive bacteria do not take up crystal violet, while gram-negative bacteria retain crystal violet. b. Gram-positive bacteria appear light red/pink after staining with safranin, while gram-negative bacteria retain crystal violet. c. Gram-positive bacteria retain crystal violet and appear light blue, while gram-negative bacteria appear purple. d. Gram-positive bacteria retain crystal violet after the decolorizing step, while gram-negative bacteria lose crystal violet and appear light red/pink