Gram positive . have a thick capsule that traps the crystal violet stain. b. have a second, outer membrane that retain the crystal violet stain. c. have a periplasmic space that traps the crystal violet. d. have multiple layers of peptidoglycan that retain the crystal violet stain.

The correct answer will be option-D

Explanation:

Gram staining is the technique developed by the Hans Christian Gram which helps differentiate the bacteria was developed in 1884.

The color of the gram stain is violet due to the presence of the crystal violet so the bacteria which will appear violet will be called gram-positive and the bacteria which will appear pinkish will be called gram-negative.

The difference in the color of the bacteria lies in the fact that the gram-positive bacteria possess peptidoglycan layers not covered with outer lipids whereas the gram-negative bacteria possess peptidoglycan layers covered with lipid layer.

The presence of many peptidoglycan layers in the gram-positive bacteria help retain the crystal violet stain and thus, option-D is the correct answer.