Here's why:

* Nucleic acids are large biomolecules responsible for storing and transmitting genetic information.

* DNA is the primary genetic material in most organisms. It contains the instructions for building and maintaining an organism.

* RNA (ribonucleic acid) is another type of nucleic acid. It plays a crucial role in protein synthesis.

While DNA and RNA are both nucleic acids, the question asks for a substance that is a nucleic acid, making DNA the correct answer.