Final answer:
Nucleic acids are the least energy-dense macromolecules compared to fats, proteins, and carbohydrates since their primary role is the storage and transmission of genetic information rather than serving as a primary energy source.
Step-by-step explanation:
Different macromolecules possess varying amounts of energy density, influencing how much energy they can provide to living organisms. Of the options provided, nucleic acids are typically the least energy dense compared to proteins, carbohydrates, and fats. This is because nucleic acids' primary function is to store and transmit genetic information rather than to provide energy. In contrast, fats have the highest energy density, followed by carbohydrates and proteins, respectively.