Dinucleotide is obtained by joining two nucleotides together by phosphodiester linkage. These linkages are present between 5’ and 3’ carbon atoms of pentose sugars of nucleotides. The 5’ carbon atom of pentose sugar in one nucleotide is attached to the 3’ carbon atom of pentose sugar of the second nucleotide. Thus, option (i) is correct.

Option (ii) is incorrect because 1’ carbon atom of pentose sugar of nucleotides is attached to the nitrogen bases.

Options (iii) and (iv) are incorrect because phosphodiester linkages are present between 5’ and 3’ carbon atoms of pentose sugars of nucleotides.