Final answer:
DNA is composed of nucleotides with a sugar-phosphate backbone and a nitrogenous base. The two strands of DNA run antiparallel to each other and are held together by covalent bonds. Complementary base pairing occurs, with adenine pairing with thymine and cytosine pairing with guanine.
Step-by-step explanation:
b. DNA is composed of nucleotides, each containing a sugar-phosphate backbone and a nitrogenous base. DNA is a double helical structure in which complementary base pairing occurs. Adenine pairs with thymine and cytosine pairs with guanine. The two individual strands of DNA are held together by covalent bonds between the phosphate of one nucleotide and sugar of the next. The two strands run antiparallel to each other.