Picturing a DNA double helix molecule as a ladder, which of the following is not a correct comparison?
A. The rungs of the ladder are comprised of A-T and G-C base pairs, which are joined by hydrogen bonds.
B. The rails of the ladder are made up of two sugar-phosphate backbones.
C. The rails of the ladder are comprised of alternating units of deoxyribose and phosphate, which are joined with covalent bonds.
D. The rungs of the ladder are comprised of the bonds between the nitrogen-containing groups.
E. The rails of the ladder are made up of a chain of alternating sugars and bases.