DNA nucleotides are attached by

✅ Explanation:
-DNA nucleotides are attached by the Hydrogen bond.
-A nucleotide is the basic unit of polynucleotide chain of DNA (deoxyribonucleic acid) or RNA (Ribonucleic acid).
-The nitrogenous bases are found in the strand's inward direction. 
-The nitrogenous bases of the two antiparallel strands form hydrogen bonds, resulting in the formation of two helical strands.
-The nitrogenous bases used in DNA (double-stranded helical structure) are adenine (A), cytosine (C), guanine (G), and thymine (T).
-Adenine is joined to thymine with two hydrogen bonds, whereas guanine is joined to cytosine by three hydrogen bonds.