Here's why:

* Hydrogen bonds are relatively weak bonds formed between a hydrogen atom covalently linked to a highly electronegative atom (like oxygen or nitrogen) and another electronegative atom.

* Nitrogenous bases in DNA have specific hydrogen bond donor and acceptor groups that allow them to pair up in a specific way:

* Adenine (A) pairs with Thymine (T) via two hydrogen bonds.

* Guanine (G) pairs with Cytosine (C) via three hydrogen bonds.

These hydrogen bonds are crucial for the stability of the DNA double helix structure. They hold the two strands of DNA together and ensure that the base pairing is correct, which is essential for accurate DNA replication and transcription.