How are nucleotides joined and what structure do the two strands make?
a) Nucleotides are joined by hydrogen bonds, and the two strands form a double helix.
b) Nucleotides are joined by covalent bonds, and the two strands form a triple helix.
c) Nucleotides are joined by ionic bonds, and the two strands form a single helix.
d) Nucleotides are joined by peptide bonds, and the two strands form a ladder-like structure.