In a single DNA strand, what type of bond links nucleotides together to form the sugar-phosphate backbone?

• A. Covalent phosphodiester bonds between the $3_{\prime }$ hydroxyl of one sugar and the $5_{\prime }$ phosphate of the next nucleotide
• B. Peptide bonds between nucleotides
• C. Hydrogen bonds between complementary nitrogenous bases (A–T and G–C)
• D. Ionic bonds between negatively charged phosphate groups and positively charged bases

Answer: (A)