Final answer:
A nucleotide is the repeating structural unit of nucleic acids, composed of a sugar, one to three phosphates, and a base.
Step-by-step explanation:
The repeating structural unit of nucleic acids, composed of a sugar, one to three phosphates, and a base, is called a nucleotide. Nucleotides are the building blocks of nucleic acids, such as DNA and RNA. Each nucleotide consists of a 5-carbon sugar, one to three phosphate groups, and a nitrogenous base.