The reason for double helical structure of DNA is the operation of: electrostatic attractions, van der Waals forces, dipole-dipole interactions, hydrogen bonding

The two polynucleotide chains or strands of DNA are linked up by hydrogen bonding between the nitrogenous base molecules of their nucleotide monomers. Adenine-Thymine (two hydrogen bonds) and Cytosine-Guanine (three hydrogen bonds). Option D is correct.