 
 <translate> To answer the above question, the relevant sentence is: Nucleotides are the building blocks of nucleic acids; they are composed of three subunit molecules: a nitrogenous base, a five-carbon sugar (ribose or deoxyribose), and at least one phosphate group.
So, the final answer is a nitrogenous base. <ibo> Iji zaa ajụjụ a dị n'elu, ahịrịokwu dị mkpa bụ: Nucleotides bụ ihe ndị na-ewu nucleic acids; ha nwere atọ subunit ụmụ irighiri ihe: a nitrogenous isi, a ise-carbon sugar (ribose ma ọ bụ deoxyribose), na ọ dịkarịa ala otu phosphate otu. N'ihi ya, azịza ya bụ na ọ bụ ihe nwere nitrogen. 