16. Which of the following is used to form covalent bonds in the sugar-phosphate backbone between fragments of DNA? O A. Ultrafiltration
O B. Restriction enzymes
O C. Centrifugation
O D. DNA ligase

hydrogen is a compound or a single element and a element is a pure substence that cannot be separated into simpler subtances

clorine is a compound its a chemical substance that forms when two or more different elements combine

so both hydrogen and clorine are compounds

examples of nucleic acids are deoxyribonucleic acid (dna) and ribonucleic acid (rna).