Select ALL correct statements about nucleic-acid structure.

### Why this is right - **Adjacent nucleotides are linked by phosphodiester bonds**: the bond connects the 3′ hydroxyl of one sugar to the 5′ phosphate of the next nucleotide. - **The base of a nucleotide is attached to its sugar by an N-glycosidic bond**: this joins the base to the pentose. - **Adenine is a purine with two rings**: purines have a fused two-ring structure. ### The concept Nucleic-acid architecture depends on distinct bonds with distinct roles: glycosidic bonds attach bases to sugars, while phosphodiester bonds build the strand backbone. The nucleotide sugar is a pentose, not a hexose. ### The other options - **The sugar in nucleotides is a hexose**: it is a pentose, containing five carbons. ### Terms - **Purine**: a two-ring nitrogenous base, including adenine and guanine. - **Phosphodiester bond**: a linkage joining nucleotides through sugar-phosphate groups. ### Remember Do not confuse the base-to-sugar bond with the sugar-to-sugar backbone linkage.