Answer:
The macromolecule that is a nucleic acid is D, an RNA molecule.
Step-by-step explanation:
Being as both DNA and RNA are nucleic acids, here is an explanation. DNA's structure is in the shape of a double-stranded helix while RNA's is structured as a single-stranded helix. DNA's backbone is made of the sugars deoxyribose and phosphate while RNA's backbone is made of the sugars ribose and phosphate. DNA also contains the bases adenine, thymine, cytosine, and guanine (adenine bonds with thymine and cytosine bonds with guanine) while RNA contains all said bases, except thymine is replaced with uracil (because of this change, the new bases pairings are adenine and uracil and still cytosine and guanine).