The primary building block (monomer) of nucleic acids is

The primary building block (monomer) of nucleic acids is the nucleotide.

Here are the steps to explain this:

1. Nucleic acids are large biomolecules essential for all known forms of life. They include DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).

2. These molecules are made up of smaller units called monomers.

3. The monomer of nucleic acids is the nucleotide.

4. Each nucleotide is composed of three parts: a sugar molecule (either ribose in RNA or deoxyribose in DNA), a phosphate group, and a nitrogenous base.

5. The nitrogenous base can be adenine (A), thymine (T), guanine (G), cytosine (C) in DNA, or adenine (A), uracil (U), guanine (G), cytosine (C) in RNA.

6. These nucleotides link together to form the structure of the nucleic acids. The phosphate group of one nucleotide bonds with the sugar molecule of the next nucleotide, creating a sugar-phosphate backbone. The nitrogenous bases stick out from this backbone and can interact with other molecules or with the nitrogenous bases of a second nucleic acid molecule.