Question

which macromolecule is the main source of energy for living things?
a. fat
b. nucleic acid
c. protein
d. carbohydrate

Explanation:

Carbohydrates are broken down into glucose, which is used as a primary energy - source by cells for various metabolic processes in living things. Fats are for long - term energy storage, nucleic acids are for genetic information, and proteins are mainly for growth, repair, and various functions like enzymes and antibodies.

Answer:

D. carbohydrate