I believe the correct answer is the fourth option. Plant cell walls consist mainly of cellulose. The cell wall of the plants provides support and other important functions. It is composed of cellulose which is classified as a carbohydrate. The plant cell wall has three layers and each layer has its own unique function.
The possible letters are A, C, G, and T, representing the four nucleotide bases of a DNA strand — adenine, cytosine, guanine, thymine — covalently linked to a phosphodiester backbone.
