[单选题]
3. Which of the foll-(db3r jzs88 vhbfvs9 owing defn6ffvnawdpl,j*h:i6 9*1 c b scribes 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.