Which of the following correctly describes the structure of DNA?

The correct description of the structure of DNA is a double helix with paired nitrogenous bases. DNA (deoxyribonucleic acid) is known for its iconic double helix shape, which consists of two long strands of nucleotides twisted around each other. Each nucleotide contains a sugar (deoxyribose), a phosphate group, and a nitrogenous base. The key feature of DNA is the pairing of nitrogenous bases: adenine pairs with thymine, and cytosine pairs with guanine. This base pairing is crucial for the structure of DNA and plays a vital role in processes such as replication and transcription.

In contrast, a single-stranded helix does not accurately represent DNA, as the molecule exists as a double-stranded structure. A ring of amino acids describes protein structures, not nucleic acids. Finally, a linear structure made of sugars only simplifies the complexity of DNA, neglecting the presence of phosphate groups and nitrogenous bases, which are essential to its overall form and function.