DNA is composed of repeating structural units called . is the five-carbon sugar found in DNA. 3 components of a nucleotide are labeled. Part A is a phosphate with 1 double-bond and single-bonds to 3 Oxygen molecules. Part B is a sugar with 5 carbon molecules. Part D is made up of nitrogen molecules.

the match duh

explanation:

the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.

a=c and then d= c because of the band so you get ac/dc and you add them together you get sound waves