Step 1: Understanding DNA replication initiation.
DNA replication begins with the separation of the two strands of the DNA double helix at the origin of replication.
Step 2: Role of initiator proteins.
Initiator proteins and helicase enzymes unwind the DNA by breaking the weak hydrogen bonds between complementary nitrogenous bases.
Step 3: Analysis of options.
(A) Glycosidic: Incorrect — links base to sugar within a nucleotide.
(B) Peptide: Incorrect — found in proteins, not DNA.
(C) Phospho-di-ester: Incorrect — forms the sugar–phosphate backbone of DNA.
(D) Hydrogen: Correct — holds complementary bases together and is broken during replication.
Step 4: Conclusion.
During DNA replication, initiator proteins break hydrogen bonds.