Nucleotides are the monomers of nucleic acids.

• A. Nucleotides
• B. Amino acids
• C. Sugars
• D. Phosphates

Answer: (A)

Nucleic acids are polymers built from repeating units called nucleotides. Each nucleotide includes a five‑carbon sugar (deoxyribose in DNA or ribose in RNA), a phosphate group, and a nitrogenous base. When nucleotides join, they form phosphodiester bonds between the sugar of one unit and the phosphate of the next, creating the sugar–phosphate backbone with the bases extending outward. This repeating nucleotide unit is what makes up DNA and RNA, so nucleotides are their monomers. The other options describe components of different macromolecules: amino acids build proteins, sugars are the monomers for carbohydrates, and phosphates are part of nucleotides but not the standalone monomer of nucleic acids.