Question

which macromolecule is the main source of energy for living things? fat nucleic acid protein carbohydrate

Explanation:

Carbohydrates are the main energy - providing macromolecules for living organisms. They are broken down during cellular respiration to release energy in the form of ATP. Proteins are mainly for building and repairing tissues, nucleic acids carry genetic information, and fats are energy - storage molecules but not the main immediate energy source.

Answer:

A. carbohydrate