(N/A) In a nucleoside,a nitrogenous base is linked to the $1^{\prime}$ position of a pentose sugar. When a phosphoric acid molecule is attached to the $5^{\prime}$ position of the sugar moiety,a nucleotide is formed. $A$ phosphodiester linkage is formed between the $3^{\prime}$ carbon of one nucleotide and the $5^{\prime}$ carbon of another nucleotide through a phosphate group. The term 'diester' indicates that the phosphate group forms two ester linkages: one with the $3^{\prime}$ hydroxyl group of one sugar and another with the $5^{\prime}$ hydroxyl group of the adjacent sugar. The acid involved in the formation of this linkage is phosphoric acid $(H_3PO_4)$.