Here's why:

* Structure: DNA is a double helix, meaning it has two strands that spiral around each other.

* Complementary Base Pairing: The two strands are held together by hydrogen bonds between specific pairs of nitrogenous bases:

* Adenine (A) pairs with Thymine (T)

* Guanine (G) pairs with Cytosine (C)

* Function: This complementary pairing allows DNA to store and transmit genetic information. One strand can act as a template for the synthesis of a new, complementary strand, ensuring accurate replication of the genetic code.

While other molecules have double stranded structures, like RNA (ribonucleic acid), DNA is the primary example that is commonly referred to as having two complementary strands.