[单选题]
3. Which of the followitc6)n5rrqe8rx) p v ;lv +tt3ang stg5(6+iv dwn7 gpr3e describes the backbone of DNA?
A. Covalent bonding between nitrogenous bases.
B. Hydrogen bonds between deoxyribose and phosphate molecules.
C. Complimentary base pairing.
D. Covalent bonds between deoxyribose and phosphate molecules.