Here's why:

* Phosphate backbone: The backbone of DNA is composed of alternating sugar (deoxyribose) and phosphate groups. Phosphate groups are highly polar due to the electronegative oxygen atoms.

* Nitrogenous bases: The nitrogenous bases (adenine, guanine, cytosine, and thymine) also contain polar groups like amino groups (-NH2) and carbonyl groups (C=O).

* Hydrogen bonding: The polar nature of DNA allows for hydrogen bonding between the bases, holding the two strands together in a double helix.

Overall, the combination of polar phosphate groups, polar bases, and hydrogen bonding makes DNA a polar molecule.