Question

a building block of dna; consists of a five-carbon sugar covalently bonded to a nitrogenous base and a phosphate group.
genome
trait
nucleotide
gene

Explanation:

The definition describes the fundamental structural unit of DNA, which is made of a deoxyribose sugar, nitrogenous base, and phosphate group. A genome is the full set of an organism's DNA; a trait is a heritable characteristic; a gene is a segment of DNA that codes for a protein. Only a nucleotide matches the given definition.

Answer:

nucleotide