The correct answers are:
(1) nitrogen bases form hydrogen bonds to their complementary bases
This is true as adenine forms a double bond with thymine and guanine forms a triple bond with guanine.
(2) sugar-phosphate chains form ion-dipole and hydrogen bonds to the aqueous surroundings
This is how the DNA is stabilized not only from inside forces but also from the environment in where the DNA is found.
(3) sugar-phosphate chains stack above each other, allowing for interaction through dispersion forces.
This is the mechanism on how the sugar-phosphate chains act as a backbone for the DNA molecule.