[单选题]
3. Which of the followin-un icf (pw58dj3e rmp (i:1gng des9vjzsx zx-gj8.h1 xz3 cribes 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.