Bond X in nucleic acid backbone

Steps:

• Identify the molecule as nucleic acid (DNA/RNA), composed of nucleotides with sugar, phosphate, and base.
• Recall bonds in nucleic acids: phosphodiester links phosphate to sugar in backbone; glycosidic links base to sugar; hydrogen bonds pair bases.
• Peptide bonds occur only in proteins, linking amino acids, not relevant to nucleic acids.
• Without diagram, bond X cannot be precisely identified, but context suggests backbone linkage.

Why D is incorrect:

• Peptide bonds form between carboxyl and amino groups of amino acids in proteins, absent in nucleic acids.

Why the others are wrong:

• A: Glycosidic bonds connect nitrogenous bases to ribose/deoxyribose sugars within nucleotides.
• B: Hydrogen bonds hold complementary bases together in double-stranded DNA/RNA.
• C: Phosphodiester bonds link adjacent nucleotides via phosphate and sugar in the chain.

Not enough information.

Final answer: Not enough information.