Here's why:

* Replication requires a template: The process of DNA replication relies on the existing DNA molecule as a template. This template provides the sequence information needed to build the new complementary strands.

* Double helix provides the template: The double helix structure of DNA allows for the separation of the two strands during replication, exposing the nucleotide bases that act as the template for new strand synthesis.

* Base pairing ensures accuracy: The complementary base pairing rules (A with T and G with C) ensure that the newly synthesized strands are accurate copies of the original template.

While single-stranded DNA (ssDNA) exists in some biological processes, it's not the form used in DNA replication.