Archaea with cell walls consisting of a thick layer of complex polysaccharides often retain crystal violet dye when stained using the Gram-staining procedure. Suggest a reason for this staining reaction

This is because of the retention of the stain by the Gram positive bacteria.

Explanation:

Gram-positive bacteria are those that can retain the Gram stain. The cell wall of this bacteria is composed of a thick peptidoglycan layer which is rich in polysaccharides like N-acetyl glucosamine and N-acetyl muramic acid.These molecules are negatively charged and and they interact with the positively charged Gram's stain.Washing with acetone or ethanol is unable to remove of the stain due to the presence of mutiple layers of peptidoglycan that prevents the stain from escaping out thereby causing the bacteria to develop the characteristic violet colour of the stain .Gram-negative bacteria are those which cannot retain the Gram stain. Their cell wall has a very thin peptidoglycan layer. Hence, they are unable to trap the positively charged stain molecules when an acetone or ethanol wash is done. On washing most of the stain gets removed causing the bacteria to retain a pinkish colour.

The answer is b. hope this !